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 A098783 #26 Jan 01 2018 21:25:28 %S A098783 0,9,1,8,2,7,3,6,4,5,18,27,36,45,54,63,72,81,90,180,91,80,92,70,93,60, %T A098783 94,50,95,40,96,30,97,20,98,10,909,181,82,71,83,61,84,51,85,41,86,31, %U A098783 87,21,88,11,809,182,73,62,74,52,75,42,76,32,77,22,78,12,709,183,64,53,65 %N A098783 Smallest integer not occurring earlier such that the concatenation of the integers has the property that the first two digits sum to 9, the next two digits also, etc. %C A098783 This sequence contains no beastly numbers (A051003). - _Rémy Sigrist_, Dec 31 2017 %H A098783 Rémy Sigrist, <a href="/A098783/b098783.txt">Table of n, a(n) for n = 0..10000</a> %H A098783 Rémy Sigrist, <a href="/A098783/a098783.gp.txt">PARI program for A098783</a> %e A098783 When parenthesis are added one can see the successive pairs of digits with sum 9: (0, 9), (1, 8), (2, 7), (3, 6), (4, 5), (18), (27), (36), (45), (54), (63), (72), (81), (90), (18)(0, 9)(1, ... - _Eric Angelini_, Dec 18 2017 %Y A098783 Cf. A051003. %K A098783 base,easy,nonn %O A098783 0,2 %A A098783 _Eric Angelini_, Oct 04 2004