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.
%I A098905 #32 Sep 08 2022 08:45:15 %S A098905 15,21,33,35,39,45,51,55,57,63,65,69,75,77,85,87,91,93,95,99,111,115, %T A098905 117,119,123,129,133,135,141,143,145,147,153,155,159,161,171,175,177, %U A098905 183,185,187,189,201,203,205,207,209,213,215,217,219,221,225,235,237 %N A098905 Odd numbers whose number of distinct prime factors is positive and even. %H A098905 G. C. Greubel, <a href="/A098905/b098905.txt">Table of n, a(n) for n = 1..1000</a> %e A098905 21 is a member of sequence because 21 is odd and number of distinct prime factors of 21, i.e., 2 is even. %t A098905 Select[Select[Range[2,400], EvenQ[PrimeNu[#]] &], OddQ] (* _G. C. Greubel_, May 09 2017 *) %t A098905 Select[Range[3,250,2],EvenQ[PrimeNu[#]]&] (* _Harvey P. Dale_, Jan 19 2020 *) %o A098905 (PARI) isok(n) = (n>1) && (n%2) && !(omega(n) % 2); \\ _Michel Marcus_, Jan 20 2020 %o A098905 (Magma) [k:k in [3..250 by 2]|IsEven(#PrimeDivisors(k))]; // _Marius A. Burtea_, Jan 20 2020 %Y A098905 Cf. A001221. %K A098905 easy,nonn %O A098905 1,1 %A A098905 _Shyam Sunder Gupta_, Oct 14 2004