OFFSET
1,1
COMMENTS
Also k for which prime(k) == 1 (mod 5). - Bruno Berselli, Mar 04 2016
The asymptotic density of this sequence is 1/4 (by Dirichlet's theorem). - Amiram Eldar, Mar 01 2021
LINKS
Zak Seidov, Table of n, a(n) for n = 1..1000
FORMULA
MATHEMATICA
Select[Range[210], Mod[Prime[ # ], 10] == 1 &] (* Ray Chandler, Nov 07 2006 *)
PROG
(Sage) [n for n in (1..300) if Mod(nth_prime(n), 10) == 1] # Bruno Berselli, Mar 04 2016
(PARI) isok(n) = !((prime(n)-1) % 10); \\ Michel Marcus, Mar 04 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended by Ray Chandler, Nov 28 2003
Formula corrected by Zak Seidov, Sep 20 2011
STATUS
approved