A068031 Number of subsets of {1,2,3,...,n} that sum to 0 mod 10.

1, 1, 1, 1, 2, 4, 7, 13, 26, 52, 104, 206, 410, 820, 1640, 3280, 6556, 13108, 26216, 52432, 104864, 209720, 419432, 838864, 1677728, 3355456, 6710896, 13421776, 26843552, 53687104, 107374208, 214748384, 429496736, 858993472, 1717986944, 3435973888, 6871947712

Offset: 0

Author

Antti Karttunen, Feb 11 2002

Keywords

• nonn

Crossrefs

10th row of A068009.

Programs

Maple

b:= proc(n, s) option remember; `if`(n=0, `if`(s=0, 1, 0),
      b(n-1, s)+b(n-1, irem(s+n, 10)))
    end:
a:= n-> b(n, 0):
seq(a(n), n=0..36);  # Alois P. Heinz, May 02 2025

Formula

Empirical G.f.: (x-1)*(2*x^7+3*x^6+4*x^5+2*x^4+2*x^3+x^2-1) / ((2*x-1)*(2*x^5-1)). - Colin Barker, Dec 22 2012