A005724 Quadrinomial coefficients.

3, 40, 546, 7728, 112035, 1650792, 24608948, 370084832, 5603730876, 85316186400, 1304770191802, 20029132137840, 308437355259930, 4762695514958640, 73716196036213800, 1143325208566357440, 17765127399780725316, 276484586847524844768, 4309270265307160983144

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

References

• L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 78.
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• R. K. Guy, Letter to N. J. A. Sloane, 1987

Crossrefs

Cf. A008287.

Programs

Maple

seq(coeff((1+x+x^2+x^3)^(2*n),x,3*n-1), n=1..30); # Robert Israel, Aug 15 2016

Formula

a(n) = A008287(2 * n, 3 * n - 1). - Sean A. Irvine, Aug 15 2016

Extensions

Offset changed by Robert Israel, Aug 15 2016