A155160 a(n) = 2^n * (n + 3)!!.

3, 16, 60, 384, 1680, 12288, 60480, 491520, 2661120, 23592960, 138378240, 1321205760, 8302694400, 84557168640, 564583219200, 6088116142080, 42908324659200, 487049291366400, 3604299271372800, 42860337640243200

Offset

0,1

Links

G. C. Greubel, Table of n, a(n) for n = 0..500

Formula

a(n) = 2^n*(n+3)!!.

From G. C. Greubel, Mar 19 2021: (Start)

a(2*n) = 2^(n-1)*(2*n+3)!/(n+1)!.

a(2*n+1) = 2^(4*n+3)*(n+2)!. (End)

Mathematica

Table[2^n*(n+3)!!, {n, 0, 30}]
Table[2^n*If[EvenQ[n], (n+3)!/(2^(n/2+1)*(n/2+1)!), 2^((n+3)/2)*((n+3)/2)!], {n, 0, 30}] (* G. C. Greubel, Mar 19 2021 *)

Prog

(Magma) [(n mod 2) eq 0 select Round(2^(n)*Factorial(n+3)/(2^(n/2+1)*Gamma((n+4)/2))) else Round(2^(n+(n+3)/2)*Gamma((n+5)/2)): n in [0..30]]; // G. C. Greubel, Mar 19 2021
(Sage) [2^n*(n+3).multifactorial(2) for n in (0..30)] # G. C. Greubel, Mar 19 2021

Crossrefs

Cf. A000079, A006882.

Sequence in context: A062474 A073999 A259056 * A370305 A355645 A323941

Adjacent sequences: A155157 A155158 A155159 * A155161 A155162 A155163

Keyword

nonn

Author

Roger L. Bagula, Jan 21 2009

Status

approved