A185715 a(n) = number of primes <= n that end in 9.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6

Offset

1,29

Comments

Partial sums of A185709.

Links

G. C. Greubel, Table of n, a(n) for n = 1..5000

A. Granville and G. Martin, Prime number races, arXiv:math/0408319 [math.NT], 2004.

A. Granville and G. Martin, Prime number races, Amer. Math. Monthly, 113 (No. 1, 2006), 1-33.

Mathematica

Accumulate[Table[If[PrimeQ[n] && Mod[n, 10] == 9, 1, 0], {n, 50}]] (* G. C. Greubel, Jul 10 2017 *)

Prog

(PARI) a(n) = sum(k=1, n, if ((k % 10)==9, isprime(k))); \\ Michel Marcus, Jul 11 2017

Crossrefs

Cf. A185705, A185706, A185708, A185709, A185711, A185712, A185714, A185715.

Sequence in context: A071839 A235044 A163857 * A111893 A121902 A087103

Adjacent sequences: A185712 A185713 A185714 * A185716 A185717 A185718

Keyword

base,nonn

Author

N. J. A. Sloane, Feb 10 2011

Status

approved