A075766 Numbers k such that A007923(k) is prime.

2, 7, 8, 10, 17, 20, 25, 28, 31, 38, 61, 62, 355, 4690, 4772, 8162, 10523, 14716

Offset

1,1

Comments

SDS(355) certified prime with Primo.

No more terms <= 8000. - XU Pingya, May 30 2017

Links

Table of n, a(n) for n=1..18.

Jason Earls, Some Results Concerning the Smarandache Deconstructive Sequence, Smarandache Notions Journal, Volume 14 Issue 1, January 2004, Pages 222-226 .

Prog

(PARI) isok(n) = my(m=(n*(n+1)/2-1)%9+1); isprime(sum(k=0, n-1, 10^k*((m-k-1)%9+1))); \\ Michel Marcus, May 30 2017

Crossrefs

Cf. A007923.

Sequence in context: A022431 A356671 A047525 * A258823 A226612 A005538

Adjacent sequences: A075763 A075764 A075765 * A075767 A075768 A075769

Keyword

more,nonn

Author

Jason Earls, Oct 09 2002

Extensions

a(14)-a(15) from XU Pingya, May 30 2017

a(16)-a(18) from Michael S. Branicky, Jun 22 2023

Status

approved