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 A374142 #19 Feb 16 2025 08:34:07 %S A374142 8,617,8726,255575,1339801,2419165,9402323,25764500,35486953, %T A374142 144568133,385495261,735503569,638279039,1183071664,1571634527, %U A374142 4449717748,3584182298,3871587494,5693954599,27084640649,24205505111,32489035067,31973745058,38935021406,47570693867,44749048300,53075499329 %N A374142 a(n) is the smallest number which can be represented as the sum of two distinct nonzero heptagonal numbers in exactly n ways, or -1 if no such number exists. %H A374142 Michael S. Branicky, <a href="/A374141/a374141.txt">Python program for A374141, A374142, and A374143</a> %H A374142 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HeptagonalNumber.html">Heptagonal Number</a> %e A374142 a(2) = 617 = 1 + 616 = 148 + 469. %o A374142 (Python) # see linked program %Y A374142 Cf. A000566, A093195, A332989, A342326, A374141, A374143. %K A374142 nonn %O A374142 1,1 %A A374142 _Ilya Gutkovskiy_, Jun 28 2024 %E A374142 a(8)-a(27) from _Michael S. Branicky_, Jun 29 2024