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 A325785 #9 Jun 07 2019 11:10:17 %S A325785 1,2,2,3,4,2,5,6,7,3,8,9,10,11,4,12,13,14,15,16,2,17,18,19,20,21,22,5, %T A325785 23,24,25,26,27,28,29,6,30,31,32,33,34,35,36,37,7,38,39,40,41,42,43, %U A325785 44,45,46,3,47,48,49,50,51,52,53,54,55,56,8,57,58,59,60,61,62,63,64,65,66,67,9,68,69,70,71,72,73,74,75,76,77,78,79,10 %N A325785 Reading the first column of this array or its successive antidiagonals is the same as reading this sequence. %C A325785 The array is always extended by its antidiagonals with the smallest term not yet present that doesn't lead to a contradiction. The sequence is thus the lexicographically earliest of its kind. %F A325785 a(n*(n+1)/2) = a(n). - _Rémy Sigrist_, May 21 2019 %e A325785 Array: %e A325785 1 2 3 5 8 12 17 23 30 38 47 ... %e A325785 2 4 6 9 13 18 24 31 39 48 58 ... %e A325785 2 7 10 14 19 25 32 40 49 59 70 ... %e A325785 3 11 15 20 26 33 41 50 60 71 83 ... %e A325785 4 16 21 27 34 42 51 61 72 84 97 ... %e A325785 2 22 28 35 43 52 62 73 85 98 112 ... %e A325785 5 29 36 44 53 63 74 86 99 113 128 ... %e A325785 6 37 45 54 64 75 87 100 114 129 145 ... %e A325785 7 46 55 65 76 88 101 115 130 146 163 ... %e A325785 3 56 66 77 89 102 116 131 147 164 182 ... %e A325785 8 67 78 90 103 117 132 148 165 183 202 ... %e A325785 ... %Y A325785 Cf. A325783 and A325784 where the same idea is developed. %Y A325785 Cf. A000217. %K A325785 tabl,nonn %O A325785 1,2 %A A325785 _Eric Angelini_, May 21 2019