May 1, 2019 posted by

ulam spiral

It is therefore no surprise that all primes other than 2 lie in alternate diagonals of the Ulam spiral. It turns out that visually following the sieve’s progress on the square spiral number line suggests a graphical and intuitive way of comprehending the diagonal dust in Ulam’s spiral of the primes. The square spiral does away with the x axis and just shows the y values, or ouput, of the quadratic equation. Upon returning home, Ulam explored his curious doodle a bit further using one of the very first powerful computers, which happened to be available to him because he was a major player at Los Alamos labs in New Mexico. Announcing the arrival of Valued Associate So think of the positive y-axis being the number line that is folded up into the spiral. Home Questions Tags Users Unanswered.

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This usually but not always consists of a repetition of a sort of stamp made up of n values that is repeated but which rotates at diagonal quadrant changes, a clear example of which is seen in the multiples of 7 above.

The image on the right is especially worth noting despite it looking like a boring checkerboard. Here are four such “fake primes” images.

Ulam spiral

Hardy and Littlewood break the product into three factors as. Recall the checkerboard of the odd numbers on the square spiral.

Ulam’s Prime Spiral Do you see the “diagonal dust”? There are many fragments of diagonal lines visible. This curve asymptotically approaches a horizontal line in the left half of the figure. When you zpiral somewhere and go out along a diagonal, with each step you increase by 8 more than you did with the previous step. See the links at the end if you’re interested. Because the primes are recursive, prime-rich functions tend to not produce multiples of small primes.


Ulam spiral – Wikipedia

It is therefore no surprise that all primes other than 2 lie in alternate diagonals of the Ulam spiral. But this is not hard because we can always figure out what fraction of the original integers remain after each culling stage. Experimenting with the Ulam Spiral Giovanna Roda. Obviously we next remove all the remaining multiples of 5 except 5. The first thousand primes Conjecture F provides a formula that can be used to estimate the density of primes along such rays.

While drawing a grid of lines, he decided upam number the intersections according to a spiral pattern, and then began circling the numbers in the spiral that were primes.

Here I am making the case that the diagonal dust is a reflection of the density of the primes on the highly diagonal remainder, or quadratic, structure that can be seen from the very beginning of running Eratosthenes’ sieve. In particular, no quadratic polynomial has ever been proved to generate infinitely many primes, much less to have a high asymptotic density of them, although there is a well-supported conjecture as to what that asymptotic density should be. Ulam’s paper associated the diagonal dust with the known fact that many simple quadratic functions produce primes for some range of inputs.


Most often, the number spiral is started with the number 1 at the center, but it spirral possible to start with any number, and the same concentration of primes along diagonal, horizontal, and vertical lines is observed.

The constant A is given by a product running over all prime numbers.

Prime Spiral

The primes, however, are the constants in the remainder structure. GeMir GeMir 1 Primality Bit Spiral Michael Schreiber. Thu Apr 18 It spirwl almost thermodynamic in nature and playing out on the odd “crystal” of the square spiraled number line.

The next number that remains is 5 and it is thus prime. This can be derived using modular arithmetic.

Now remove all multiples of 3 except 3 itself. Part of this diagonal is shown in the spiral below, with blue background corresponding to primes, green to squares of prime numbers, and red to numbers with 25 or more divisors. With each removal cycle of another prime’s multiples, the prime density on the remainder structure goes up and this happens fast enough that the diagonal quality of the earliest remainder structure is never completely eroded.

Some even assert this figure shows a hidden structure in the primes. The City and the Stars. The primes being a kind of mathematical honey pot, the diagonal dust in his spiral has led to much discussion of the reason for the clearly visible pattern despite the lack of predictability in the primes.

Images of the spiral up to 65, points were displayed on “a scope attached to the machine” and then photographed.