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 A077342 #7 Dec 05 2013 19:55:52 %S A077342 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,200,21,22,23,24,25, %T A077342 26,27,28,29,300,310,32,33,34,35,36,37,38,39,400,410,420,43,44,45,46, %U A077342 47,48,49,500,510,520,530,54,55,56,57,58,59,600,610,620,630,640,65,66,67 %N A077342 First column of A077341. %C A077342 a(20) = 200 and not 20. Can anyone derive a formula for a(n)? %C A077342 a(n) = n when n > 10 * floor(n/10) + floor(n/10) - 2. Otherwise it is guaranteed that n has appeared in a previous row of the triangle. - _Alonso del Arte_, Jan 07 2013 %H A077342 Hans Havermann, <a href="/A077342/b077342.txt">Table of n, a(n) for n = 1..10000</a> %Y A077342 Cf. A077339, A077340, A077341, A077343. %K A077342 base,easy,nonn %O A077342 1,2 %A A077342 _Amarnath Murthy_, Nov 05 2002