A088421 Number of primes in arithmetic progression starting with 5 and with d=2n.

2, 1, 5, 2, 1, 5, 2, 1, 4, 1, 1, 3, 2, 1, 1, 2, 1, 2, 2, 1, 5, 1, 1, 5, 1, 1, 4, 2, 1, 1, 2, 1, 3, 2, 1, 1, 2, 1, 2, 1, 1, 4, 1, 1, 1, 2, 1, 5, 2, 1, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 5, 1, 1, 4, 2, 1, 1, 1, 1, 3, 2, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 3, 2, 1, 1, 1, 1, 2, 2, 1, 3, 2, 1, 1, 1

Offset: 1

Author

Zak Seidov, Sep 29 2003

Keywords

• easy
• nonn

Comments

Arithmetic progression is stopped when next term is not prime. E.g. for n=3, a=5, that is 5,11,17,23,29 are prime, while next term, 35, is not prime.

Crossrefs

Cf. A088420, A088422, A088423, A088424, A088425, A088426, A088427, A088428, A088429.

Programs

Mathematica

bb={}; Do[s=1; Do[If[PrimeQ[5+k*d], s=s+1, bb={bb, s}; Break[]], {k, 10}], {d, 2, 200, 2}]; Flatten[bb]