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 A260235 #7 Jun 23 2017 19:01:14 %S A260235 2,2,2,2,3,2,3,2,3,3,3,2,3,3,2,3,4,2,4,3,3,3,3,2,4,2,4,3,4,2,3,4,3,4, %T A260235 3,2,4,4,3,2,4,3,4,3,4,3,4,2,4,3,3,4,3,3,4,3,4,3,5,2,4,3,2,4,4,3,4,3, %U A260235 4,3,4,3,4,3,3,4,5,2,4,3,3,4,4,3,4,3 %N A260235 Number of distinct prime factors of the n-th hexagonal number (A000384). %H A260235 Colin Barker, <a href="/A260235/b260235.txt">Table of n, a(n) for n = 2..1000</a> %F A260235 a(n) = A001221(A000384(n)). %e A260235 a(6) = 3 because A000384(6) = 66 = 2 * 3 * 11. %t A260235 PrimeNu[PolygonalNumber[6,Range[2,90]]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jun 23 2017 *) %o A260235 (PARI) %o A260235 pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number %o A260235 a(n) = omega(pg(6, n)) %Y A260235 Cf. A000384, A001221, A260233, A260234, A260236. %K A260235 nonn %O A260235 2,1 %A A260235 _Colin Barker_, Jul 20 2015