A124941 Numbers k such that k and k+4 are 4-almost primes.

36, 56, 84, 100, 132, 136, 152, 228, 340, 344, 372, 376, 472, 484, 488, 532, 546, 564, 568, 580, 621, 632, 686, 708, 770, 804, 808, 820, 846, 852, 856, 868, 872, 950, 1012, 1192, 1204, 1206, 1208, 1274, 1304, 1326, 1336, 1444, 1524, 1550, 1572, 1576, 1690

Offset

1,1

Links

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

Example

36=2^2*3^2, 40=2^3*5; 56=2^3*7, 60=2^2*3*5.

Mathematica

Select[Range[1690], PrimeOmega[#]==PrimeOmega[#+4]==4 &] (* James C. McMahon, Dec 07 2024 *)

Prog

(PARI) isok(n) = (bigomega(n) == 4) && (bigomega(n+4) == 4); \\ Michel Marcus, Oct 11 2013

Crossrefs

Cf. A014613, A124940, A124942, A157483, A180117.

Sequence in context: A242343 A243540 A336384 * A116321 A187989 A080469

Adjacent sequences: A124938 A124939 A124940 * A124942 A124943 A124944

Keyword

nonn

Author

Zak Seidov, Nov 13 2006

Status

approved