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 A374143 #28 Feb 16 2025 08:34:07 %S A374143 9,1053,12641,68141,365641,953181,2830641,6232341,13969041,23211261, %T A374143 104733741,84994021,175873641,159851141,538547641,602713041,810204416, %U A374143 1019740041,1053265741,1972957241,3339356041,5914492241,6886737541,6388758241,8902368041,7858982841,4942246941,18439299341,26639916441 %N A374143 a(n) is the smallest number which can be represented as the sum of two distinct nonzero octagonal numbers in exactly n ways, or -1 if no such number exists. %H A374143 Michael S. Branicky, <a href="/A374143/b374143.txt">Table of n, a(n) for n = 1..38</a> %H A374143 Michael S. Branicky, <a href="/A374141/a374141.txt">Python program for A374141, A374142, and A374143</a> %H A374143 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/OctagonalNumber.html">Octagonal Number</a> %e A374143 a(2) = 1053 = 8 + 1045 = 408 + 645. %o A374143 (Python) # see linked program %Y A374143 Cf. A000567, A093195, A332989, A342326, A374141, A374142. %K A374143 nonn %O A374143 1,1 %A A374143 _Ilya Gutkovskiy_, Jun 28 2024 %E A374143 a(9)-a(29) from _Michael S. Branicky_, Jun 29 2024