A076209 Numbers k such that (k!! + (k+1)!! - 1)/2 is prime.

2, 3, 4, 5, 28, 35, 61, 75, 218, 267, 395, 844, 1509, 2122, 4157, 14707, 19996, 21483, 22450

Offset

1,1

Links

Table of n, a(n) for n=1..19.

Crossrefs

Cf. A006882 (double factorials), A076208, A076210, A076211.

Sequence in context: A115337 A114333 A265098 * A037399 A220891 A220890

Adjacent sequences: A076206 A076207 A076208 * A076210 A076211 A076212

Keyword

nonn,more

Author

Zak Seidov, Nov 02 2002

Extensions

a(9)-a(15) (checked k < 5000) from Hugo Pfoertner, Jun 22 2003

a(16)-a(19) from Michael S. Branicky, Jul 09 2025

Status

approved