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A364339

G.f. satisfies A(x) = (1 + x) * (1 + x*A(x)^6).

1, 2, 13, 150, 1978, 28603, 438273, 6992052, 114915180, 1932233883, 33081722359, 574755965137, 10107627041697, 179576579730534, 3218352405778284, 58114340679967608, 1056284029850962674, 19310039426151335622, 354818596435147647654, 6549556302551204621664, 121394125733645986376838

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OFFSET

0,2

LINKS

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

FORMULA

a(n) = Sum_{k=0..n} binomial(6*k+1,k) * binomial(6*k+1,n-k) / (6*k+1).

MATHEMATICA

terms = 21; A[_] = 0; Do[A[x_] = (1+x)(1+x*A[x]^6) + O[x]^terms // Normal, terms]; CoefficientList[A[x], x] (* Stefano Spezia, Mar 24 2025 *)

PROG

(PARI) a(n) = sum(k=0, n, binomial(6*k+1, k)*binomial(6*k+1, n-k)/(6*k+1));

CROSSREFS