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 A115906 #11 Apr 06 2023 08:30:43
%S A115906 1,2,5,7,9,16,144,186,410,656,680,805,963,968,1152,1331,1419,1476,
%T A115906 1557,1608,2158,2220,2376,2401,2529,2840,3376,3447,3570,3591,4018,
%U A115906 5030,5769,5967,6530,6720,6854,6955,7250,7856,8004,8514,8946,9144
%N A115906 Numbers k such that k + sigma(k) + phi(k) is a triangular number.
%H A115906 Amiram Eldar, <a href="/A115906/b115906.txt">Table of n, a(n) for n = 1..10000</a>
%e A115906 1331 + sigma(1331) + phi(1331) = 4005 = T(89).
%o A115906 (PARI) isok(n) = {my(f=factor(n)); ispolygonal(n + sigma(f) + eulerphi(f), 3);} \\ _Amiram Eldar_, Apr 06 2023
%Y A115906 Cf. A000010, A000203, A000217, A069066, A115904, A115905.
%K A115906 nonn
%O A115906 1,2
%A A115906 _Giovanni Resta_, Feb 06 2006