OFFSET
1,2
PROG
(PARI) isp(n) = isprime(6*n+1); \\ A167021
a(n) = sum(k=1, n, isp(k)); \\ Michel Marcus, Feb 06 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Jan 25 2010
EXTENSIONS
Entries checked by R. J. Mathar, Apr 24 2010
STATUS
approved