OFFSET
1,1
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..10000
MATHEMATICA
Position[#, 3] &@ Table[k = 1; While[! PrimeQ[k n + 1], k++]; k, {n, 500}] // Flatten (* Michael De Vlieger, Mar 02 2017 *)
PROG
(PARI) is(n)=!isprime(n+1)&&!isprime(2*n+1)&&isprime(3*n+1) \\ M. F. Hasler, May 13 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected by R. J. Mathar, Jul 26 2015
Name edited by M. F. Hasler, May 13 2018
STATUS
approved