A176258 - OEIS

A176258

Numbers of the form 4k+1 with greatest prime divisor of the form 4m-1.

9, 21, 33, 49, 57, 69, 77, 81, 93, 105, 121, 129, 133, 141, 161, 165, 177, 189, 201, 209, 213, 217, 237, 245, 249, 253, 285, 297, 301, 309, 321, 329, 341, 345, 361, 381, 385, 393, 413, 417, 437, 441, 453, 465, 469, 473, 489, 497, 501, 513, 517, 525, 529, 537, 553, 573

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OFFSET

1,1

COMMENTS

All terms of A107978 are in the sequence.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[4 Range@ 150 + 1, Mod[#, 4] == 3 &[FactorInteger[#][[-1, 1]]] &] (* Michael De Vlieger, Feb 07 2016 *)

PROG

(PARI) isok(n) = (n != 1) && ((n % 4) == 1) && ((vecmax(factor(n)[, 1]) % 4) == 3); \\ Michel Marcus, Feb 07 2016

CROSSREFS