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%I #10 Mar 24 2022 12:48:05
%S 2,3,5,7,11,13,17,19,23,29,31,-37,41,43,47,53,-59,61,-67,71,73,79,83,
%T 89,97,-101,-103,107,109,113,127,-131,137,139,-149,151,-157,163,167,
%U 173,179,181,191,193,197,199,211,223,227,229,-233,239,241,251,-257,-263
%N a(n) = -prime(n) if prime(n) is an irregular prime else prime(n).
%t regularQ[p_] := And @@ ( !Divisible[ Numerator[ BernoulliB[#]], p] & /@ Range[2, p - 3, 2]); Table[p = Prime[n]; If[ regularQ[p], p, -p], {n, 1, 56}] (* _Jean-François Alcover_, Jul 02 2013 *)
%o (Sage)
%o def A226159_list(len):
%o t = [0]*(len+1); t[0] = 1; L = [2]; p = 1
%o for m in (1..len):
%o q = m + 1; t[m] = 1 / q
%o for j in range(m, 0, -1) :
%o t[j - 1] = (t[j - 1] - t[j]) * j
%o if 2.divides(m):
%o if q.divides(denominator(t[0])):
%o if q.divides(p): q = -q
%o L.append(q)
%o p *= numerator(t[0])
%o return L
%o A226159_list(263)
%Y Cf. A000040, A000928.
%K sign
%O 1,1
%A _Peter Luschny_, Jun 27 2013
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