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 A325784 #12 Jun 07 2019 11:09:24 %S A325784 1,2,3,3,4,5,3,6,7,8,4,9,10,11,12,5,13,14,15,16,17,3,18,19,20,21,22, %T A325784 23,6,24,25,26,27,28,29,30,7,31,32,33,34,35,36,37,38,8,39,40,41,42,43, %U A325784 44,45,46,47,4,48,49,50,51,52,53,54,55,56,57,9,58,59,60,61,62,63,64,65,66,67,68,10,69,70,71,72,73,74,75,76,77,78,79,80,11 %N A325784 Reading the first row of this array or its successive antidiagonals is the same as reading this sequence. %C A325784 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 A325784 a(n*(n-1)/2 + 1) = a(n). - _Rémy Sigrist_, May 21 2019 %e A325784 Array: %e A325784 1 2 3 3 4 5 3 6 7 8 4 ... %e A325784 3 4 6 9 13 18 24 31 39 48 58 ... %e A325784 5 7 10 14 19 25 32 40 49 59 70 ... %e A325784 8 11 15 20 26 33 41 50 60 71 83 ... %e A325784 12 16 21 27 34 42 51 61 72 84 97 ... %e A325784 17 22 28 35 43 52 62 73 85 98 112 ... %e A325784 23 29 36 44 53 63 74 86 99 113 128 ... %e A325784 30 37 45 54 64 75 87 100 114 129 145 ... %e A325784 38 46 55 65 76 88 101 115 130 146 163 ... %e A325784 47 56 66 77 89 102 116 131 147 164 182 ... %e A325784 57 67 78 90 103 117 132 148 165 183 202 ... %e A325784 ... %Y A325784 Cf. A325783 and A325785 where the same idea is developed. %Y A325784 Cf. A000124. %K A325784 nonn,tabl %O A325784 1,2 %A A325784 _Eric Angelini_, May 21 2019