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A336572 G.f. A(x) satisfies: A(x) = 1 + x * A(x)^4 * (1 +  2 * A(x)). 3
1, 3, 42, 822, 18708, 464115, 12175368, 332156784, 9328004700, 267870927324, 7829893576878, 232189300430454, 6968123350684692, 211232335919261178, 6458598626291716128, 198949096401788859636, 6168233789851179030684, 192334850789654814053700, 6027727888877572168027368 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..655

FORMULA

a(n) = Sum_{k=0..n} 2^k * binomial(n,k) * binomial(4*n+k+1,n)/(4*n+k+1).

a(n) = (1/(4*n+1)) * Sum_{k=0..n} 2^(n-k) * binomial(4*n+1,k) * binomial(5*n-k,n-k).

MATHEMATICA

a[n_] := Sum[2^k * Binomial[n, k] * Binomial[4*n + k + 1, n]/(4*n + k + 1), {k, 0, n}];  Array[a, 19, 0] (* Amiram Eldar, Jul 27 2020 *)

PROG

(PARI) {a(n) = local(A=1+x*O(x^n)); for(i=0, n, A=1+x*A^4*(1+2*A)); polcoeff(A, n)}

(PARI) {a(n) = sum(k=0, n, 2^k*binomial(n, k)*binomial(4*n+k+1, n)/(4*n+k+1))}

(PARI) {a(n) = sum(k=0, n, 2^(n-k)*binomial(4*n+1, k)*binomial(5*n-k, n-k))/(4*n+1)} \\ Seiichi Manyama, Jul 26 2020

CROSSREFS

Column k=4 of A336574.

Cf. A243667, A336540.

Sequence in context: A097068 A269046 A092470 * A206820 A157542 A078601

Adjacent sequences:  A336569 A336570 A336571 * A336573 A336574 A336575

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Jul 25 2020

STATUS

approved

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Last modified January 17 10:48 EST 2021. Contains 340214 sequences. (Running on oeis4.)