A055579 a(n) = binomial(12*n-1,3*n-1)/((6*n-1)*(12*n-1)).

1, 133, 39556, 16112057, 7772368380, 4168218286276, 2403705165816240, 1461462393790971585, 925088518413937893358, 604420266372219374357644, 405139322689963395796890100, 277349882927724253636179972980

Offset

1,2

Comments

This sequence satisfies a(n) = A000260(3n-1)/3. - F. Chapoton, Sep 08 2023

Links

Table of n, a(n) for n=1..12.

C. O. Oakley and R. J. Wisner, Flexagons, Amer. Math. Monthly 64 (1957), 143-154, see p. 151.

Mathematica

Table[Binomial[12n-1, 3n-1]/((6n-1)(12n-1)), {n, 20}] (* Harvey P. Dale, Nov 02 2011 *)

Prog

(PARI) a(n) = binomial(12*n-1, 3*n-1)/((6*n-1)*(12*n-1)); \\ Michel Marcus, Sep 29 2017

Crossrefs

Cf. A000260.

Sequence in context: A129049 A281496 A015264 * A191715 A208626 A061491

Adjacent sequences: A055576 A055577 A055578 * A055580 A055581 A055582

Keyword

nonn

Author

N. J. A. Sloane, Aug 24 2000

Status

approved