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 A052474 #13 Jul 09 2025 03:53:59 %S A052474 1,2,4,7,12,13,14,15,16,18,20,21,22,23,32,35,36,39,42,48,49,50,51,53, %T A052474 54,57,58,59,61,62,64,66,68,76,77,78,80,82,86,87,89,91,92,93,98,103, %U A052474 109,110,118,124,127,128,129,132,133,135,136,139,140,141,142,143,149 %N A052474 Construct difference array so that (1) first row begins with 1, (2) every row is monotonic increasing, (3) no number appears more than once, (4) smallest number not yet used begins a new row. Sequence gives main diagonal. %H A052474 Reinhard Zumkeller, <a href="/A052474/b052474.txt">Table of n, a(n) for n = 1..150</a> %e A052474 Array begins %e A052474 1 3 9 26 73 194 ... %e A052474 .2 6 17 47 121 ... %e A052474 . 4 11 30 74 ... %e A052474 .. 7 19 44 ... %e A052474 ... 12 25 ... %e A052474 .... 13 ... %o A052474 (Haskell) %o A052474 a052474 n = a056230_tabl !! (n-1) !! 0 %o A052474 -- _Reinhard Zumkeller_, Nov 19 2011 %Y A052474 Cf. A057153 (first row), A057154 (numbers not used), A056230 (array), A056231, A056232, A056233, A056234. %K A052474 nice,nonn,easy %O A052474 1,2 %A A052474 _Jonas Wallgren_, Jul 30 2000