A004395 Ratios of successive terms are 1,1,2,3,3,4,5,5,6,7,7,...

1, 1, 1, 2, 6, 18, 72, 360, 1800, 10800, 75600, 529200, 4233600, 38102400, 342921600, 3429216000, 37721376000, 414935136000, 4979221632000, 64729881216000, 841488455808000, 11780838381312000, 176712575719680000

Offset

0,4

Links

Robert Israel, Table of n, a(n) for n = 0..431

Formula

G.f.: hypergeom([1/2, 1/2, 1, 1], [], 8*x^3) + x*hypergeom([1/2, 1, 1, 3/2], [], 8*x^3) + x^2*hypergeom([1, 1, 3/2, 3/2], [], 8*x^3). - Robert Israel, Aug 05 2020

Conjecture D-finite with recurrence 243*a(n) -216*a(n-1) +54*(-2*n+3)*a(n-2) +6*(-12*n^3+60*n^2-87*n+28)*a(n-3) +4*(2*n-5)*(2*n-7)*(n-3)*a(n-4)=0. - R. J. Mathar, Sep 14 2025

Maple

G:=hypergeom([1/2, 1/2, 1, 1], [], 8*x^3) + x*hypergeom([1/2, 1, 1, 3/2], [], 8*x^3) + x^2*hypergeom([1, 1, 3/2, 3/2], [], 8*x^3):
S:= series(G, x, 41):
seq(coeff(S, x, n), n=0..40); # Robert Israel, Aug 05 2020

Crossrefs

a(n+1) = a(n) * A004396(n).

Sequence in context: A364849 A194088 A022491 * A277862 A213427 A006388

Adjacent sequences: A004392 A004393 A004394 * A004396 A004397 A004398

Keyword

nonn

Author

N. J. A. Sloane

Status

approved