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A227868 Composite numbers congruent to 7 or 23 (mod 30). 0
143, 187, 203, 217, 247, 323, 413, 427, 473, 517, 533, 623, 637, 667, 697, 713, 803, 817, 833, 847, 893, 923, 1027, 1043, 1057, 1073, 1133, 1147, 1177, 1207, 1253, 1267, 1313, 1343, 1357, 1387, 1403, 1417, 1463, 1477, 1507, 1537, 1643 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It is remarkable that up to 4913, numbers congruent to 7 or 23 (mod 30) are more frequently prime than composite.

LINKS

Table of n, a(n) for n=1..43.

PROG

(PARI) for(p=1, 1999, setsearch([7, 23], p%30)&&!isprime(p)&&print1(p", "))

CROSSREFS

Cf. A132237, A229947.

Sequence in context: A217141 A097435 A073954 * A176876 A257767 A158136

Adjacent sequences:  A227865 A227866 A227867 * A227869 A227870 A227871

KEYWORD

nonn

AUTHOR

M. F. Hasler, Nov 02 2013

STATUS

approved

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Last modified October 17 01:03 EDT 2019. Contains 328103 sequences. (Running on oeis4.)