cp's OEIS Frontend

A309403 Total sum of the number of divisors of the element sum over all nonempty subsets of [n].

%I A309403 #13 Mar 24 2022 03:58:59
%S A309403 1,5,16,40,96,217,469,1011,2147,4497,9389,19489,40256,82948,170413,
%T A309403 349158,714153,1458199,2972683,6052561,12308971,25006177,50755272,
%U A309403 102933086,208594116,422432018,854956112,1729360940,3496259940,7065053883,14270420877,28812580857
%N A309403 Total sum of the number of divisors of the element sum over all nonempty subsets of [n].
%H A309403 Alois P. Heinz, <a href="/A309403/b309403.txt">Table of n, a(n) for n = 1..650</a>
%p A309403 b:= proc(n, s) option remember; `if`(n=0,
%p A309403       numtheory[tau](s), b(n-1, s)+b(n-1, s+n))
%p A309403     end:
%p A309403 a:= n-> b(n, 0):
%p A309403 seq(a(n), n=1..30);
%t A309403 b[n_, s_] := b[n, s] = If[n == 0,
%t A309403      If[s == 0, 0, DivisorSigma[0, s]], b[n-1, s] + b[n-1, s+n]];
%t A309403 a[n_] := b[n, 0];
%t A309403 Table[a[n], {n, 1, 30}] (* _Jean-François Alcover_, Mar 24 2022, after _Alois P. Heinz_ *)
%Y A309403 Row sums of A309402.
%Y A309403 Cf. A000005, A309281.
%K A309403 nonn
%O A309403 1,2
%A A309403 _Alois P. Heinz_, Jul 28 2019