cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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

This page as a plain text file.
%I A145192 #7 Jun 02 2025 00:38:17
%S A145192 141,421,479,596,629,746,801,804,904,966,981,1016,1042,1051,1119,1121,
%T A145192 1142,1146,1154,1261,1289,1296,1324,1329,1384,1399,1406,1454,1471,
%U A145192 1493,1499,1560,1576,1597,1637,1646
%N A145192 Integers n for which Omega(6n-1)>2 and Omega(6n+1)>2.
%H A145192 Harvey P. Dale, <a href="/A145192/b145192.txt">Table of n, a(n) for n = 1..10000</a>
%e A145192 (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.
%t A145192 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]]]
%t A145192 Select[Range[2000],PrimeOmega[6#+1]>2&&PrimeOmega[6#-1]>2&] (* _Harvey P. Dale_, Apr 26 2016 *)
%Y A145192 Cf. A001222.
%K A145192 nonn
%O A145192 1,1
%A A145192 _Arran Fernandez_, Oct 03 2008