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%I #10 Mar 07 2020 00:39:18
%S 1,1,2,1,5,1,2,10,2,10,13,5,1,10,2,10,13,5,37,2,34,1,50,34,17,1,25,13,
%T 10,65,2,41,65,53,5,29,34,10,1,50,2,74,10,26,5,85,106,5,25,13,1,10,26,
%U 2,61,37,34,17,5,1,26,13,170,10,2,5,130,58,125,106,73,130,50,26,170
%N a(n) is the least number m such that A002313(n)*m - 1 is a square.
%C A002313 has the 4k+1 and 4k+2 primes.
%C Related to Stormer numbers.
%H J. Todd, <a href="https://www.jstor.org/stable/2305526">A problem on arc tangent relations</a>, Amer. Math. Monthly, 56 (1949), 517-528.
%F a(n) = ((A002314(n-1))^2 + 1) / A002313(n).
%e a(3) = 2 because A002313(3)=13 and 13*2-1 = 5^2.
%Y Cf. A002313, A002314, A005528.
%K nonn
%O 1,3
%A _N. J. A. Sloane_
%E Edited by _Don Reble_, Apr 13 2006
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