A043296 - OEIS

%I #19 Jun 03 2021 14:28:53

%S 6,3,6,3,12,12,6,6,24,6,12,12,6,15,12,6,6,30,6,12,15,15,12,15,12,15,

%T 24,15,12,42,6,6,21,3,24,21,6,3,15,6,21,15,6,12,21,6,6,24,6,12,15,15,

%U 12,30,15,24,6,15,6,39,6,3,42,6,24,24,6,6,30,33,6,42,6,15,21,3,12,42,6,6

%N Sum of digits of denominator of Bernoulli number B(2n).

%F a(n) = A007953(A002445(n)). - _Michel Marcus_, Feb 16 2021

%e Denominator(B(2*9))=798 and 7+9+8=24 hence a(9)=24.

%t Total[IntegerDigits[#]]&/@Denominator[BernoulliB[2*Range[80]]] (* _Harvey P. Dale_, Jul 02 2017 *)

%o (PARI) a(n) = sumdigits(denominator(bernfrac(2*n))); \\ _Michel Marcus_, Feb 16 2021

%o (Python)

%o from sympy import bernoulli

%o def a(n): return sum(map(int, str(bernoulli(2*n).denominator())))

%o print([a(n) for n in range(1, 81)]) # _Michael S. Branicky_, Jun 03 2021

%Y Cf. A002445, A007953, A043295.

%K base,easy,nonn

%O 1,1

%A _Benoit Cloitre_, Mar 24 2002