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Number of subsets of {1,2,3,...,n} that sum to 0 mod 13.
1

%I #13 Sep 08 2022 13:31:47

%S 1,1,1,1,1,2,5,10,20,39,79,158,316,632,1262,2522,5042,10082,20164,

%T 40330,80660,161320,322638,645278,1290556,2581112,5162224,10324444,

%U 20648884,41297764,82595524,165191048,330382100,660764200,1321528400

%N Number of subsets of {1,2,3,...,n} that sum to 0 mod 13.

%F Empirical G.f.: -(2*x^13-x^10+x^9-x^6+x^4+x^3+x^2+x-1) / ((2*x-1)*(2*x^13-1)). [_Colin Barker_, Dec 22 2012]

%t Table[Count[Subsets[Range[n]], _?(Divisible[Total[#], 13]&)], {n,20}] (* _Harvey P. Dale_, Feb 14 2012 *)

%Y 13th row of A068009.

%K nonn

%O 0,6

%A _Antti Karttunen_, Feb 11 2002