A124792 Numbers n such that n and A001414(n) are 3-almost primes.

18, 42, 50, 78, 92, 110, 130, 138, 154, 164, 222, 230, 236, 266, 282, 284, 285, 338, 357, 366, 370, 374, 404, 425, 426, 429, 430, 438, 452, 555, 574, 582, 590, 596, 602, 605, 610, 637, 638, 654, 668, 682, 710, 754, 764, 782, 814, 826, 854, 874, 894, 908, 938

Offset

1,1

Comments

Cf. A014612 = 3-almost primes, A001414 = sopfr(n).

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

8 is not here because 8=2*2*2=>2+2+2=6=2*3 (semiprime),
12 is not here because 12=2*2*3=>2+2+3=7 (prime),
18 is here because 18=2*3*3=>2+3+3=8=2*2*2 (3-almost prime),
20, 27, 28, 30, are not here,
42 is here because 42=2*3*7=>2+3+7=12=2*2*3 (3-almost prime).

Prog

(PARI) is(n)=my(f=factor(n)); sum(i=1, #f~, f[i, 2])==3 && bigomega(sum(i=1, #f~, f[i, 1]*f[i, 2]))==3 \\ Charles R Greathouse IV, Oct 11 2013

Crossrefs

Cf. A001414, A014612.

Sequence in context: A097972 A154284 A174264 * A090605 A318168 A175152

Adjacent sequences: A124789 A124790 A124791 * A124793 A124794 A124795

Keyword

nonn

Author

Zak Seidov, Nov 07 2006

Status

approved