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A214664 The x-coordinates of prime numbers in an Ulam spiral oriented counterclockwise with first step east. 17

%I #13 Apr 01 2022 09:13:59

%S 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,

%T -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,

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

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

%C 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.

%H William Rex Marshall, <a href="/A214664/b214664.txt">Table of n, a(n) for n = 1..10077</a> (coordinates of primes in a 325 X 325 square).

%H Scientific American, <a href="https://www.jstor.org/stable/24936037">Front Matter</a>, Vol. 210, No. 3, March 1964.

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

%K sign,easy

%O 1,5

%A _William Rex Marshall_, Jul 26 2012

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Last modified March 28 17:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)