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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, 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 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: A009439 A000233 A002624 * A188123 A081661 A005103 Adjacent sequences:  A068036 A068037 A068038 * A068040 A068041 A068042 KEYWORD nonn AUTHOR Antti Karttunen, Feb 11 2002 STATUS approved

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