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A369478

Expansion of (1/x) * Series_Reversion( x / ((1+x)^2 * (1+x+x^2)^2) ).

1, 4, 24, 170, 1320, 10868, 93197, 823484, 7445184, 68545882, 640446224, 6057249180, 57878746750, 557903174040, 5418441862824, 52971933934834, 520869559359424, 5147999004530720, 51113415228327827, 509583784051748692, 5099262428810825568

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..20.

Index entries for reversions of series

FORMULA

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

PROG

(PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/((1+x)^2*(1+x+x^2)^2))/x)

(PARI) a(n, s=2, t=2, u=2) = sum(k=0, n\s, binomial(t*(n+1), k)*binomial((t+u)*(n+1)-k, n-s*k))/(n+1);

CROSSREFS

Cf. A219537, A369480.

Cf. A143927, A369477.

Cf. A369441.

Sequence in context: A374659 A221088 A365225 * A368975 A366980 A378883

Adjacent sequences: A369475 A369476 A369477 * A369479 A369480 A369481

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Jan 23 2024

STATUS

approved

URL: https://oeis.org/A369478

⇱ A369478 - OEIS