A338373 Numbers k such that bigomega(2*k + 1) >= 4.

40, 67, 94, 112, 121, 148, 157, 175, 187, 202, 220, 229, 247, 256, 262, 283, 292, 310, 312, 337, 346, 364, 367, 382, 391, 409, 412, 418, 427, 437, 445, 472, 487, 499, 514, 517, 526, 535, 544, 553, 562, 577, 580, 598, 607, 612, 634, 637, 643, 652

Offset: 1

Author

Davide Rotondo, Oct 23 2020

Keywords

• nonn

Comments

Numbers of the form k + A336263(m) + 2*k*A336263(m) where k and m are positive integers. If a term d in A336263 is not here, bigomega(2*d + 1) = 3.

Examples

			13 is in A336263, therefore 1 + 13 + 2*13*1 = 40 is a term, and (40*2) + 1 = 81 is not the product of 3 prime numbers.
		

Links

• Dumitru Damian, Table of n, a(n) for n = 1..30000

Crossrefs

Cf. A001222, A336263, A159919.

Programs

Mathematica

Select[Range[650], PrimeOmega[2*# + 1] >= 4 &] (* Amiram Eldar, Oct 24 2020 *)

PARI

isok(k) = bigomega(2*k+1) >= 4; \\ Michel Marcus, Oct 24 2020