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Greatest prime factor of |A001067(n)|, or 1 if |A001067(n)| = 1.
1

%I #22 Mar 12 2017 00:33:46

%S 1,1,1,1,1,691,1,3617,43867,617,593,2294797,657931,362903,1001259881,

%T 305065927,151628697551,26315271553053477373,154210205991661,

%U 1897170067619,1520097643918070802691,1798482437,67568238839737,153289748932447906241,47464429777438199

%N Greatest prime factor of |A001067(n)|, or 1 if |A001067(n)| = 1.

%F a(n) = A006530(|A001067(n)|).

%F If n = A112548(m)/2, a(n) = |A001067(n)|.

%e |A001067(10)| = 174611 = 283*617. So a(10) = 617.

%e |A001067(16)| = 7709321041217 = 37*683*305065927. So a(16) = 305065927.

%t Table[FactorInteger[Abs@ Numerator[BernoulliB[2 n]/(2 n)]][[-1, 1]], {n, 25}] (* _Michael De Vlieger_, Jan 21 2017 *)

%o (PARI) a(n) = if(abs(numerator(bernfrac(2*n) / (2*n))) == 1, 1, vecmax(factor(abs(numerator(bernfrac(2*n) / (2*n))))[,1]));

%o for(n=1, 25, print1(a(n), ", ")) \\ _Indranil Ghosh_, Mar 11 2017

%Y Cf. A000928, A001067, A006530, A033563, A112548, A281331.

%K nonn

%O 1,6

%A _Seiichi Manyama_, Jan 20 2017

%E a(20)-a(25) from _Michael De Vlieger_, Jan 21 2017