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 A079214 #4 Mar 30 2012 18:51:39 %S A079214 10,1010,1210,101010,101210,121010,121210,123210,10101010,10101210, %T A079214 10121010,10121210,10123210,12101010,12101210,12121010,12121210, %U A079214 12123210,12321010,12321210,12323210,12343210,1010101010,1010101210 %N A079214 Catalan paths: numbers starting with 1 and ending with 0 where each digit is nonnegative and adjacent digits differ by 1. %C A079214 a(23713) cannot easily be written in decimal. %F A079214 a(n) =A079215(n)-(10^ceiling[log_10(A079215(n))]-1)/9. %e A079214 Can be constructed from A063171 by (starting from a notional leading 0) adding 1 to previous digit of a(n) if next digit of A063171 is 1 and subtracting 1 if next digit is 0: e.g. A063171(3)=1100, so digits of a(3) are 0+1=1, 1+1=2, 2-1=1 and 1-1=0 giving a(3)=1210. %Y A079214 Cf. A063171, A079215. a(n) has A000108(m) values with 2m digits. %K A079214 base,nonn %O A079214 1,1 %A A079214 _Henry Bottomley_, Jan 02 2003