A052278 a(n) = (4n+3)!/4^n.

6, 1260, 2494800, 20432412000, 475176173472000, 25246110096567360000, 2658415393168543008000000, 501882242076289234480320000000, 157671325170687025904337331200000000, 77811744999685071405945898971187200000000, 57616484702466807973246700352205274112000000000

Offset

0,1

Links

Table of n, a(n) for n=0..10.

Formula

From Amiram Eldar, Feb 25 2022: (Start)

Sum_{n>=0} 1/a(n) = (sinh(sqrt(2)) - sin(sqrt(2)))/(4*sqrt(2)).

Sum_{n>=0} (-1)^n/a(n) = (cosh(1)*sin(1) - sinh(1)*cos(1))/4. (End)

Mathematica

Table[(4n+3)!/4^n, {n, 0, 20}] (* Harvey P. Dale, Mar 14 2020 *)

Prog

(PARI) a(n) = (4*n+3)!/4^n; \\ Michel Marcus, Feb 25 2022

Crossrefs

Cf. A052277.

Sequence in context: A001324 A183585 A060706 * A264103 A202381 A067510

Adjacent sequences: A052275 A052276 A052277 * A052279 A052280 A052281

Keyword

nonn

Author

N. J. A. Sloane, Feb 05 2000

Status

approved