A145192 Integers n for which Omega(6n-1)>2 and Omega(6n+1)>2.

141, 421, 479, 596, 629, 746, 801, 804, 904, 966, 981, 1016, 1042, 1051, 1119, 1121, 1142, 1146, 1154, 1261, 1289, 1296, 1324, 1329, 1384, 1399, 1406, 1454, 1471, 1493, 1499, 1560, 1576, 1597, 1637, 1646

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..10000

Example

(6*141)-1 = 845, which has >2 prime factors (counted with multiplicity), namely 5,13 and 13. (6*141)+1 = 847, which has >2 prime factors (counted with multiplicity), namely 7,11 and 11. So 141 is in the sequence.

Mathematica

For[x = 6, x < 10001, x += 6, If[PrimeQ[x - 1] == True, y = "P", S = 0; F = FactorInteger[x - 1]; For[k = 1, k < Length[F] + 1, k++, S += F[[k]][[2]]]; If[S == 2, y = "A", y = "N"]]; If[PrimeQ[x + 1] == True, z = "P", S = 0; F = FactorInteger[x + 1]; For[k = 1, k < Length[F] + 1, k++, S += F[[k]][[2]]]; If[S == 2, z = "A", z = "N"]]; If[y == "N" && z == "N", Print[x/6]]]
Select[Range[2000], PrimeOmega[6#+1]>2&&PrimeOmega[6#-1]>2&] (* Harvey P. Dale, Apr 26 2016 *)

Crossrefs

Cf. A001222.

Sequence in context: A031892 A389702 A063373 * A228597 A255154 A068046

Adjacent sequences: A145189 A145190 A145191 * A145193 A145194 A145195

Keyword

nonn

Author

Arran Fernandez, Oct 03 2008

Status

approved