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

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

Offset: 0

Author

N. J. A. Sloane, Feb 05 2000

Keywords

• nonn

Crossrefs

Cf. A052277.

Programs

Mathematica

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

PARI

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

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)