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

1,1

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

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 *)

Prog

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

Crossrefs

Sequence in context: A086000 A155544 A221974 * A081703 A166391 A339863

Adjacent sequences: A227866 A227867 A227868 * A227870 A227871 A227872

Keyword

nonn

Author

M. F. Hasler, Nov 02 2013

Status

approved