A108627 - OEIS

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A108627

Logarithmic g.f.: Sum_{n>=1} a(n)/n*x^n = log(G108626(x)), where G108626(x) is g.f. for A108626.

2, 6, 20, 66, 222, 750, 2536, 8578, 29018, 98166, 332092, 1123458, 3800630, 12857438, 43496400, 147147266, 497795634, 1684030566, 5697034596, 19272929986, 65199855118, 220569529934, 746181374904, 2524313509762

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OFFSET

1,1

COMMENTS

A108626 forms the antidiagonal sums of square array A108625, in which row n equals the crystal ball sequence for A_n lattice.

LINKS

Table of n, a(n) for n=1..24.

FORMULA

G.f.: A(x) = 2*x*(1 - x - x^3)/(1 - 4*x + 2*x^2 + x^4).

PROG

(PARI) a(n)=polcoeff(2*x*(1-x-x^3)/(1-4*x+2*x^2+x^4+x*O(x^n)), n)

(PARI) /* Logarithm of g.f. of A108626: */ a(n)=n*polcoeff(log(sum(k=0, n, sum(j=0, k, sum(i=0, j, binomial(k-j, i)^2*binomial(k-i, j-i)))*x^k)+x*O(x^n)), n)

CROSSREFS

Cf. A108625, A108626.

Sequence in context: A052991 A246019 A226510 * A193234 A285197 A372872

Adjacent sequences: A108624 A108625 A108626 * A108628 A108629 A108630

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jun 13 2005

STATUS

approved