A068039 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,7

LINKS

Table of n, a(n) for n=0..35.

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]

CROSSREFS

18th row of A068009.

Sequence in context: A293358 A227265 A295960 * A188123 A081661 A005103

Adjacent sequences: A068036 A068037 A068038 * A068040 A068041 A068042

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 11 2002

STATUS

approved