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 A027669 #19 Feb 27 2025 10:48:07 %S A027669 3,4,6,8,10,11,14,17,20,23,26,29,30,32,35,38,41,43,44,47,50,53,56,59, %T A027669 60,62,65,68,71,74,77,80,83,86,88,89,92,95,98,101,104,107,110,113,116, %U A027669 119,122,125,128,131,134,137,140,143,145,146,149,152,155,158,161,164,167,170,173,176,179,182,185,188,191,194,197,200,203,206,209,212,215,218,221,224,227,230,233,236,239,242,245,248,251,254,257,260,263,266,269,272,275,276 %N A027669 Numbers k such that for some m, the sum of the first m k-gonal numbers is again a k-gonal number. %C A027669 The m-th k-gonal number is m+(k-2)*(m^2-m)/2. %C A027669 3*j+2 = A016789(j) is a term for j >= 2. %F A027669 Set union of A027696 and A016789, excluding elements 2 and 5. - _Max Alekseyev_, Feb 27 2025 %Y A027669 Cf. A016789, A027696, A344410. %K A027669 nonn %O A027669 1,1 %A A027669 Masanobu Kaneko (mkaneko(AT)math.kyushu-u.ac.jp) %E A027669 More terms from _Max Alekseyev_, Feb 27 2025