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 A108554 Main diagonal of square array A108553, in which row n equals the crystal ball sequence for D_n lattice. 3
 1, 3, 13, 147, 1681, 18733, 204205, 2195399, 23429185, 249258777, 2650436845, 28209301211, 300745906449, 3212758605189, 34392151363021, 368908132170511, 3964622452867329, 42682164804034609, 460242445806795853 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Limit a(n+1)/a(n) ~ 11.08... LINKS PROG (PARI) {a(n)=if(n<0, 0, if(n==0, 1, if(n==1, 3, sum(j=0, n, binomial(2*n-j, n-j)* (binomial(2*n, 2*j)-2*j*(n-j)*binomial(n, j)/(n-1))))))} CROSSREFS Cf. A108553, A108555. Sequence in context: A130589 A041591 A001150 * A287029 A339025 A317074 Adjacent sequences:  A108551 A108552 A108553 * A108555 A108556 A108557 KEYWORD nonn AUTHOR Paul D. Hanna, Jun 10 2005 STATUS approved

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Last modified August 9 18:55 EDT 2022. Contains 356026 sequences. (Running on oeis4.)