A172103 - OEIS

A172103

Partial sums of A167020 where A167020(n)=1 iff 6*n-1 is prime.

1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9, 10, 10, 11, 12, 12, 13, 14, 15, 15, 15, 16, 17, 17, 18, 18, 18, 19, 20, 21, 21, 22, 23, 23, 23, 23, 23, 24, 25, 26, 26, 27, 28, 29, 30, 30, 31, 31, 32, 32, 32, 33, 34, 34, 34, 34, 34, 35, 36, 37, 37, 37, 37, 38, 39, 39, 40, 40, 40, 41, 41, 42, 42

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OFFSET

1,2

COMMENTS

Where A167020 is the characteristic sequence: A167020(n)=1 iff 6*n-1 is prime.

LINKS

Table of n, a(n) for n=1..73.

MATHEMATICA

Accumulate[Table[If[PrimeQ[6 n-1], 1, 0], {n, 100}]] (* Harvey P. Dale, Dec 27 2022 *)

PROG

(PARI) ism(n) = isprime(6*n-1); \\ A167020

a(n) = sum(k=1, n, ism(k)); \\ Michel Marcus, Feb 06 2019