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 A076940 #2 Dec 05 2013 19:55:47 %S A076940 1010,10100,101000,1001000,10100000,100100000,1000100000,1010000000, %T A076940 10010000000,100010000000,10000010000000,10100000000,1010000, %U A076940 1000100000000,100000100000000,10000000100000000 %N A076940 Define a mapping for a reduced rational number p/q by f(p/q) = 1 followed by p zeros followed by a 1 followed by q zeros. %C A076940 (p,q) = 1, p = A066657(n) and q = A066658(n). %C A076940 This gives another proof that rational numbers are countable. %F A076940 a(n) = 10^(p+q+1)+ 10^q where p = A066657(n) and q = A066658(n) %Y A076940 Cf. A066657, A066658. %K A076940 nonn %O A076940 1,1 %A A076940 _Amarnath Murthy_, Oct 19 2002