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A355365

Central terms of A355360; a(n) = A355360(2*n,n).

1, 3, 54, 1360, 41405, 1404102, 51126740, 1957600876, 77812428681, 3183756066040, 133302637049516, 5687179333193904, 246453229359401883, 10821674290217357756, 480561612716912592360, 21549547977144582750304, 974600584933918611940825, 44409401763058366474029057

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OFFSET

0,2

LINKS

Paul D. Hanna, Table of n, a(n) for n = 0..60

FORMULA

a(n) ~ c * d^n / n^2, where d = 51.3157915205364... and c = 0.1124829020506... - Vaclav Kotesovec, Mar 19 2023

PROG

(PARI) {a(n) = my(A=[1, y], t); for(i=1, 2*n, A=concat(A, 0); t = ceil(sqrt(2*(#A)+9));

A[#A] = polcoeff( x*y*Ser(A) - sum(m=-t, t, (-1)^m*x^(m*(m+1)/2)*Ser(A)^m ), #A-1)); polcoeff(A[2*n+1], n, y)}

for(n=0, 30, print1( a(n), ", "));

CROSSREFS