A109705 Number of partitions of n into parts each equal to 3 mod 7.

1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 2, 3, 1, 2, 4, 2, 2, 4, 4, 2, 4, 5, 3, 4, 6, 5, 4, 6, 7, 5, 6, 8, 8, 6, 9, 11, 7, 9, 13, 10, 9, 14, 14, 10, 15, 17, 14, 15, 19, 19, 16, 20, 24, 20, 21, 27, 27, 22, 29, 33, 27, 30, 38, 35, 32, 41, 44, 37, 43, 51, 47, 45

Offset: 0

Author

Erich Friedman, Aug 07 2005

Keywords

• nonn

Examples

			a(20)=2 because we have 20=17+3=10+10.
		

Links

• Vaclav Kotesovec, Table of n, a(n) for n = 0..10000

Programs

Maple

g:=1/product(1-x^(3+7*j),j=0..20): gser:=series(g,x=0,90): seq(coeff(gser,x,n),n=0..87); # Emeric Deutsch, Apr 14 2006

Mathematica

nmax=100; CoefficientList[Series[Product[1/(1-x^(7*k+3)),{k, 0, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Feb 27 2015 *)

Formula

G.f.: 1/product(1-x^(3+7j), j=0..infinity). - Emeric Deutsch, Apr 14 2006

a(n) ~ Gamma(3/7) * exp(Pi*sqrt(2*n/21)) / (2^(12/7) * 3^(3/14) * 7^(2/7) * Pi^(4/7) * n^(5/7)) * (1 + (23*Pi/(168*sqrt(42)) - 15*sqrt(3/14)/(7*Pi)) / sqrt(n)). - Vaclav Kotesovec, Feb 27 2015, extended Jan 24 2017

a(n) = (1/n)*Sum_{k=1..n} A284444(k)*a(n-k), a(0) = 1. - Seiichi Manyama, Mar 28 2017

Extensions

Changed offset to 0 and added a(0)=1 by Vaclav Kotesovec, Feb 27 2015