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A024720 a(n) = (1/4)*(3 + Sum_{k=0..n} C(4k,k)). 0

%I #13 May 10 2020 14:58:22

%S 1,2,9,64,519,4395,38044,334054,2963629,26499449,238414581,2155749364,

%T 19572882981,178326272881,1629509263831,14928031562011,

%U 137059765831906,1260847661188318,11618870102584178,107234108018545278

%N a(n) = (1/4)*(3 + Sum_{k=0..n} C(4k,k)).

%F G.f.: (2*g-3)*g^4/((3*g-4)*(1-g+g^4)) where g = 1+x*g^4 is the g.f. of A002293. - _Mark van Hoeij_, Nov 11 2011

%o (PARI) a(n) = (3+sum(k=0, n, binomial(4*k, k)))/4; \\ _Michel Marcus_, May 10 2020

%Y Cf. A002293.

%K nonn

%O 0,2

%A _Clark Kimberling_

%E More terms from _James A. Sellers_, May 01 2000

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Last modified March 28 15:28 EDT 2024. Contains 371254 sequences. (Running on oeis4.)