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, 32114, 117712
Offset: 1
Links
- Jason Earls, Some Results Concerning the Smarandache Deconstructive Sequence, Smarandache Notions Journal, Volume 14 Issue 1, January 2004, Pages 222-226.
- Shyam Sunder Gupta, Primes in the Smarandache deconstructive sequence, Scientia Magna Vol. 2 (2006), No. 3, 26-30. Reports the three probable primes for k= 4690, 4772, and 8162.
- Shyam Sunder Gupta, Memorable Prime, Number Theory Mailing List, Mar 07 2024. Reports the 32114-digit prime.
Crossrefs
Cf. A007923.
Programs
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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
Extensions
a(14)-a(15) from XU Pingya, May 30 2017
a(16)-a(18) from Michael S. Branicky, Jun 22 2023
a(19) from Michael S. Branicky, Nov 18 2024
a(20) from Michael S. Branicky, Jun 12 2025
Comments