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A227869 Composite numbers congruent to 7 (mod 30). 2
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 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..45.

MATHEMATICA

Select[Table[30n + 7, {n, 100}], Not[PrimeQ[#]] &] (* Alonso del Arte, Nov 03 2013 *)

PROG

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

CROSSREFS

Sequence in context: A086000 A155544 A221974 * A081703 A166391 A029556

Adjacent sequences:  A227866 A227867 A227868 * A227870 A227871 A227872

KEYWORD

nonn

AUTHOR

M. F. Hasler, Nov 02 2013

STATUS

approved

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Last modified August 22 00:43 EDT 2019. Contains 326169 sequences. (Running on oeis4.)