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 A128373 #7 Aug 26 2022 16:53:19 %S A128373 4,7,8,11,13,16,19,12,22,26,29,34,37,43,46,53,17,18,56,64,67,76,79,89, %T A128373 92,103,106,118,23,25,121,134,137,151,154,169,172,188,191,208,24,211, %U A128373 229,30,33,232,251,254,274,277,298,301,323,326,349,352,376,379,404,38 %N A128373 Irregular triangle read by rows: row n (n>=2) lists positions in the sequence A007318 where n appears. %e A128373 In A007318, the number 2 appears in position 4, so the first row is 4. The number 3 appears in positions 7 and 8 in A007318, so the second row is 7, 8. %e A128373 The irregular triangle begins: %e A128373 4 %e A128373 7, 8 %e A128373 11, 13 %e A128373 16, 19 %e A128373 12, 22, 26 %e A128373 29, 34 %e A128373 37, 43 %e A128373 46, 53 %e A128373 ... %Y A128373 Cf. A003015, A003016, A007318, A059233. %K A128373 easy,nonn,tabf %O A128373 2,1 %A A128373 _Nick Hobson_, Mar 01 2007