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 A113941 #8 Mar 12 2015 19:17:45 %S A113941 35,247,1247,2501,4187,15251,17767,33227,49051,63551,68587,71177, %T A113941 76501,81317,96647,112477,118301,128627,147737,159251,182527,241001, %U A113941 250717,265651,302177,318551,438751,485357,563347,655051,1563151,1600117 %N A113941 Pentagonal numbers (A000326) that are also brilliant numbers (A078972). %C A113941 This is to pentagonal numbers A000326 as A113940 is to triangular numbers A000217. These may be seen as the 5th and 3rd row of an infinite array of k-gonal numbers which are also brilliant numbers, where the 4th row is A001248 squares of primes. - _Jonathan Vos Post_, Apr 05 2009 %F A113941 A000326 INTERSECTION A078972. %e A113941 a(1) = 35 = 5th pentagonal number = 5*(3*5-1)/2 = 5 * 7, with the two prime factors each being one digit in length. a(2) = 247 = 13th pentagonal number = 13*(3*13-1)/2 = 13 * 19, with the two prime factors each being two digits in length. a(6) = 15251 = 101 * 151, with the two prime factors each being three digits in length. - _Jonathan Vos Post_, Apr 05 2009 %e A113941 17767 is the 109th pentagonal number and 17767=109*163 is brilliant. %Y A113941 Cf. A000326, A078972, A159190. %Y A113941 Cf. A001222, A001248, A001358, A113940, A114439. %K A113941 base,nonn %O A113941 1,1 %A A113941 _Giovanni Resta_, Jan 31 2006 %E A113941 Edited by _N. J. A. Sloane_, Apr 07 2009 at the suggestion of R. J. Mathar %E A113941 Two more terms from _R. J. Mathar_, Apr 06 2009