A227869 Composite numbers congruent to 7 (mod 30).

187, 217, 247, 427, 517, 637, 667, 697, 817, 847, 1027, 1057, 1147, 1177, 1207, 1267, 1357, 1387, 1417, 1477, 1507, 1537, 1687, 1717, 1807, 1837, 1897, 1927, 1957, 2047, 2077, 2107, 2167, 2197, 2227, 2257, 2317, 2407, 2497, 2527, 2587, 2737, 2827, 2947, 2977

Offset: 1

Author

M. F. Hasler, Nov 02 2013

Keywords

• nonn

Comments

Up to 4897, there are more primes than composites among the numbers of the form 7+30k, only from 4927 on, composite numbers become more frequent.

See A132231 for primes of that form. See also A132237 (primes = 7 or 23 (mod 30)) and A229947 (primes not = 7 or 23 (mod 30)).

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Programs

Mathematica

Select[Table[30n + 7, {n, 100}], Not[PrimeQ[#]] &] (* Alonso del Arte, Nov 03 2013 *)
Select[Range[7,3000,30],CompositeQ] (* Harvey P. Dale, Oct 09 2023 *)

PARI

forstep(p=7,1999,30,isprime(p)||print1(p","))