%I #10 Feb 26 2013 12:16:09
%S 8,10,172,12,168,19,19,21,21,168,14,37,37,14,18,30,68,10,10,4,10,4,29,
%T 29,32,2484,58,30,32,2484,76,16,10,10,18,23,23,1861,1861,30,34,958,
%U 126,22,10,182,10,10,74,10,112,26,48,29,29,774,13,13,26,774,18,10
%N Number of different Gaussian primes in the Gaussian prime spiral beginning at the n-th positive real Gaussian prime (A002145).
%C The Gaussian prime spiral is described in the short note by O'Rourke and Wagon. It is not known if every iteration is a closed loop. See A222298 for the number of line segments between primes.
%D Joseph O'Rourke and Stan Wagon, Gaussian prime spirals, Mathematics Magazine, vol. 86, no. 1 (2013), p. 14.
%H T. D. Noe, <a href="/A222299/b222299.txt">Table of n, a(n) for n = 1..1000</a>
%e The loop beginning with 31 is {31, 43, 43 - 8i, 37 - 8i, 37 - 2i, 45 - 2i, 45 - 8i, 43 - 8i, 43, 47, 47 - 2i, 45 - 2i, 45 + 2i, 47 + 2i, 47, 43, 43 + 8i, 45 + 8i, 45 + 2i, 37 + 2i, 37 + 8i, 43 + 8i, 43, 31, 31 + 4i, 41 + 4i, 41 - 4i, 31 - 4i, 31}. But only 19 are unique.
%t loop2[n_] := Module[{p = n, direction = 1}, lst = {n}; While[While[p = p + direction; ! PrimeQ[p, GaussianIntegers -> True]]; direction = direction*(-I); AppendTo[lst, p]; ! (p == n && direction == 1)]; Length[Union[lst]]]; cp = Select[Range[1000], PrimeQ[#, GaussianIntegers -> True] &]; Table[loop2[p], {p, cp}]
%K nonn
%O 1,1
%A _T. D. Noe_, Feb 25 2013