A071842 Number of primes == 7 mod 8 <= n.

0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 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, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7

Offset

1,23

Links

Table of n, a(n) for n=1..105.

Mathematica

Table[If[PrimeQ[n]&&Mod[n, 8]==7, 1, 0], {n, 120}]//Accumulate (* Harvey P. Dale, Feb 11 2018 *)

Prog

(PARI) for(n=1, 200, print1(sum(i=1, n, if((i*isprime(i)-7)%8, 0, 1)), ", "))

Crossrefs

Sequence in context: A071840 A000193 A059939 * A344517 A371355 A085141

Adjacent sequences: A071839 A071840 A071841 * A071843 A071844 A071845

Keyword

easy,nonn

Author

Benoit Cloitre, Jun 08 2002

Status

approved