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A004395 Ratios of successive terms are 1,1,2,3,3,4,5,5,6,7,7,... 2
1, 1, 1, 2, 6, 18, 72, 360, 1800, 10800, 75600, 529200, 4233600, 38102400, 342921600, 3429216000, 37721376000, 414935136000, 4979221632000, 64729881216000, 841488455808000, 11780838381312000, 176712575719680000 (list; graph; refs; listen; history; text; internal format)
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

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: A177472 A194088 A022491 * A277862 A213427 A006388

Adjacent sequences:  A004392 A004393 A004394 * A004396 A004397 A004398

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified February 24 18:55 EST 2021. Contains 341584 sequences. (Running on oeis4.)