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A049511
Numbers k such that prime(k) == 1 (mod 10).
9
5, 11, 13, 18, 20, 26, 32, 36, 42, 43, 47, 53, 54, 58, 60, 64, 67, 79, 82, 83, 89, 94, 98, 100, 105, 110, 115, 116, 121, 125, 126, 133, 135, 141, 142, 152, 156, 160, 164, 167, 172, 173, 177, 178, 182, 190, 193, 194, 197, 202, 210, 212, 216, 218, 221, 230, 233
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
FORMULA
a(n) = A000720(A030430(n)). - Ray Chandler, Nov 07 2006
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
EXTENSIONS
Extended by Ray Chandler, Nov 28 2003
Formula corrected by Zak Seidov, Sep 20 2011
STATUS
approved