A292759 Expansion of e.g.f. exp(x)*(tan x + sec x)^3.

1, 4, 16, 67, 304, 1519, 8386, 51007, 340024, 2469859, 19438606, 164899447, 1500636844, 14587478299, 150891959026, 1655133221887, 19192311085264, 234597922978339, 3015167371458646, 40651421300224327, 573707768015267284, 8458761578948943979, 130059537979390701466

Offset: 0

Author

N. J. A. Sloane, Sep 26 2017

Keywords

• nonn

Links

• C. K. Cook, M. R. Bacon, and R. A. Hillman, Higher-order Boustrophedon transforms for certain well-known sequences, Fib. Q., 55(3) (2017), 201-208.

Crossrefs

Cf. A000667, A292756.

Programs

Mathematica

nmax = 20; CoefficientList[Series[Exp[x]*(Tan[x]+Sec[x])^3, {x, 0, nmax}], x] * Range[0, nmax]! (* Vaclav Kotesovec, Jun 02 2019 *)

Formula

a(n) ~ 2^(n + 11/2) * n^(n + 5/2) / (Pi^(n + 5/2) * exp(n - Pi/2)). - Vaclav Kotesovec, Jun 02 2019