A068039 Number of subsets of {1,2,3,...,n} that sum to 0 mod 18.

1, 1, 1, 1, 1, 1, 3, 8, 16, 30, 58, 115, 229, 456, 912, 1824, 3643, 7286, 14572, 29132, 58262, 116522, 233024, 466048, 932096, 1864150, 3728300, 7456600, 14913112, 29826220, 59652436, 119304704, 238609408, 477218816, 954437292, 1908874584

Offset: 0

Author

Antti Karttunen, Feb 11 2002

Keywords

• nonn

Crossrefs

18th row of A068009.

Formula

Empirical G.f.: -(12*x^35 +2*x^34 -16*x^33 +8*x^32 +16*x^31 -6*x^30 +2*x^29 +12*x^28 +16*x^27 -8*x^26 -32*x^25 -18*x^24 +6*x^23 +16*x^22 +6*x^21 +2*x^20 +12*x^19 -12*x^18 -6*x^17 -x^16 +8*x^15 -4*x^14 -8*x^13 +3*x^12 -x^11 -6*x^10 +4*x^8 +6*x^7 +x^6 +x^5 +x^4 -3*x^3 -x^2 -x +1) / ((2*x -1)*(2*x^3 -1)*(2*x^6 -1)*(2*x^9 -1)*(2*x^18 -1)). [Colin Barker, Dec 23 2012]