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A068041 Number of subsets of {1,2,3,...,n} that sum to 0 mod 20. 1
1, 1, 1, 1, 1, 1, 2, 6, 14, 26, 52, 103, 205, 410, 820, 1640, 3278, 6554, 13108, 26216, 52432, 104860, 209716, 419432, 838864, 1677728, 3355448, 6710888, 13421776, 26843552, 53687104, 107374192, 214748368, 429496736, 858993472, 1717986944 (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.: (x-1)^2*(4*x^12+4*x^11-x^10-7*x^9-11*x^8-15*x^7-15*x^6-11*x^5-5*x^4-2*x^3+x+1) / ((2*x-1)*(2*x^5-1)). [Colin Barker, Dec 22 2012]

CROSSREFS

20th row of A068009.

Sequence in context: A212964 A279742 A068042 * A182155 A101586 A178080

Adjacent sequences:  A068038 A068039 A068040 * A068042 A068043 A068044

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 11 2002

STATUS

approved

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Last modified July 22 07:23 EDT 2019. Contains 325216 sequences. (Running on oeis4.)