A214664 The x-coordinates of prime numbers in an Ulam spiral oriented counterclockwise with first step east.

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

Offset: 1

Author

William Rex Marshall, Jul 26 2012

Keywords

• sign
• easy

Comments

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

Links

• William Rex Marshall, Table of n, a(n) for n = 1..10077 (coordinates of primes in a 325 X 325 square).
• Scientific American, Front Matter, Vol. 210, No. 3, March 1964.

Crossrefs

Cf. A000040, A063826, A214665, A214666, A214667.