A214666 The x-coordinates of prime numbers in an Ulam spiral oriented counterclockwise with first step west.

-1, -1, 1, 1, -2, -2, 2, 2, 0, -3, -3, 3, 3, 3, -1, -4, -2, 0, 4, 4, 4, -2, -5, -5, 1, 5, 5, 5, 5, 3, -6, -6, -2, 0, 6, 6, 6, 0, -4, -7, -7, -7, 1, 3, 7, 7, 7, -5, -8, -8, -8, -8, -8, 2, 8, 8, 8, 8, 4, 0, -2, -9, -9, -5, -3, 1, 9, 9, 5, 3, -1, -7, -10, -10, -10

Offset: 1

Author

William Rex Marshall, Jul 26 2012

Keywords

• sign
• easy

Comments

The eight possible orientations of the Ulam spiral can be derived from combining either A214664 or A214666 with either A214665 or A214667 as ordered pairs of coordinates.

This spiral is rotated 180 degrees from the spiral on the March 1964 cover of Scientific American.

Links

• William Rex Marshall, Table of n, a(n) for n = 1..10077 (coordinates of primes in a 325 X 325 square)

Crossrefs

Cf. A000040, A063826, A214664, A214665, A214667.