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%I #6 Mar 29 2015 19:11:31
%S 7,9,7,1,3,1,9,7,3,7,3,1,3,3,7,1,7,3,9,9,1,9,1,3,1,3,7,1,3,1,7,7,7,7,
%T 3,7,3,7,9,1,7,3,9,3,7,3,1,7,1,7,1,3,7,9,1,1,7,9,7,1,7,9,3,1,1,1,7,9,
%U 1,3,3,1,7,9,7,9,3,1,7,1,7,9,7,7,1,9,9,9,3,9,3,9,7,9,3,9,1,7,3,9,1,3,3,9,7
%N Residues modulo 10 of the irregular primes (A000928).
%D Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966, pp. 425-430 (but there are errors).
%e a(6) = 1 because the 6th irregular prime is 131.
%t fQ[n_] := Block[{p = n, k = 1}, While[ 2*k <= p - 3 && Mod[ Numerator[ BernoulliB[ 2*k ]], p ] != 0, k++ ]; 2k != p - 1]; Mod[ Select[ Prime[ Range[2, 275]], fQ[ # ] &], 10] (* _Robert G. Wilson v_, Dec 10 2004 *)
%Y Cf. A000928.
%K easy,nonn
%O 1,1
%A _Pahikkala Jussi_, Dec 04 2004
%E More terms from _Robert G. Wilson v_, Dec 10 2004
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