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 A109750 #12 Aug 05 2023 04:12:33 %S A109750 66,78,120,4095,491536,523776 %N A109750 Admirable triangular numbers. %C A109750 No further term between 523776 and 4050045000. - _R. J. Mathar_, Feb 11 2008 %C A109750 a(7) > 10^20, if it exists. - _Amiram Eldar_, Aug 05 2023 %F A109750 A111592 INTERSECT A000217. - _R. J. Mathar_, Feb 11 2008 %e A109750 a(1) = 66 because 11*(11+1)/2 = 66 and 1+2+3+11+22+33-6 = 66. %t A109750 admQ[n_] := (ab = DivisorSigma[1, n] - 2 n) > 0 && EvenQ[ab] && ab/2 < n && Divisible[n, ab/2]; Select[Accumulate[Range[1024]], admQ] (* _Amiram Eldar_, Aug 05 2023 *) %Y A109750 Cf. A000217, A111592. %K A109750 nonn,more %O A109750 1,1 %A A109750 _Jason Earls_, Aug 11 2005