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 A338105 #22 Feb 16 2025 08:34:00 %S A338105 9,96,1330,4725,21021,22400,421515,675675,5370365,576576,10790325, %T A338105 39255125,51548805,7286400,978624647,144729585,649593945,125245120, %U A338105 1109593485,4519064403,13908638315,253955520,8860666815,30587913125,33144736086,859541760,147839441750 %N A338105 a(n) is the least integer that can be expressed as the difference of two n-gonal numbers in exactly n ways. %C A338105 a(17) <= 1340770739, a(18) = 144729585, a(19) <= 9381302307, a(20) <= 1257818848, a(21) <= 6299438145, a(22) <= 32911706919, a(23) <= 26720105555, a(24) <= 3141537984, a(25) <= 59558175105, a(26) <= 71119743695, a(27) <= 260207700831, a(28) <= 28582652736, a(29) <= 688883385190, a(30) <= 593086020813. - _Chai Wah Wu_, Oct 14 2020 %H A338105 Martin Ehrenstein, <a href="/A338105/b338105.txt">Table of n, a(n) for n = 3..40</a> %H A338105 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PolygonalNumber.html">Polygonal Number</a> %H A338105 <a href="/index/Pol#polygonal_numbers">Index to sequences related to polygonal numbers</a> %e A338105 a(3) = 9 because 9 = 10 - 1 = 15 - 6 = 45 - 36 and this is the least integer that can be expressed as the difference of two triangular numbers in exactly 3 ways. %Y A338105 Cf. A038547, A068314, A072502, A257411, A334034, A334035, A334036, A334037. %K A338105 nonn %O A338105 3,1 %A A338105 _Ilya Gutkovskiy_, Oct 10 2020 %E A338105 a(11)-a(16) from _Chai Wah Wu_, Oct 13 2020 %E A338105 a(17) and a(19)-a(40) from _Martin Ehrenstein_, Oct 23 2020