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 A333914 #6 Apr 09 2020 23:49:47 %S A333914 3,4,5,6,7,8,3,10,11,12,4,14,15,16,5,18,3,20,6,22,23,24,7,26,27,28,4, %T A333914 30,31,32,9,3,35,36,10,38,5,40,11,42,43,44,12,46,47,48,6,50,51,52,14, %U A333914 4,3,56,15,58,7,60,16,62,63,64,17,66,67,68,8,70,71,72,19,5,75,76,20,78,9 %N A333914 a(n) is the least integer m >= 3 such that n is m-gonal pyramidal number. %H A333914 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PyramidalNumber.html">Pyramidal Number</a> %H A333914 <a href="/index/Ps#pyramidal_numbers">Index to sequences related to pyramidal numbers</a> %e A333914 a(18) = 5 since 18 is a pentagonal pyramidal number, but not a square pyramidal or tetrahedral number. %Y A333914 Cf. A080851, A176774, A261720. %K A333914 nonn %O A333914 4,1 %A A333914 _Ilya Gutkovskiy_, Apr 09 2020