A088423 a(n) is the number of primes in arithmetic progression starting with 11 and with d = 2n.

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

Offset

1,1

Comments

Arithmetic progression is stopped when next term is not prime. E.g., for n=3, a=4, that is 11,17,23,29 are prime, while next term, 35, is not prime.

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Mathematica

bb={}; Do[s=1; Do[If[PrimeQ[11+k*d], s=s+1, bb={bb, s}; Break[]], {k, 10}], {d, 2, 200, 2}]; Flatten[bb]

Prog

(PARI) a(n) = my(p=11, x=p+2*n, i=1); while(1, if(ispseudoprime(x), i++; x=x+2*n, return(i))) \\ Felix Fröhlich, May 28 2021

Crossrefs

Cf. A088420, A088421, A088422, A088424, A088425, A088426, A088427, A088428, A088429.

Sequence in context: A031424 A013942 A187816 * A006839 A268267 A205395

Adjacent sequences: A088420 A088421 A088422 * A088424 A088425 A088426

Keyword

easy,nonn

Author

Zak Seidov, Sep 29 2003

Status

approved