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 A083811 #6 Aug 23 2014 13:06:53 %S A083811 36,396,3996,39996,399996,3999996,39999996,399999996,3999999996, %T A083811 39999999996,399999999996,3999999999996 %N A083811 Numbers n such that 2n+1 is the digit reversal of n+1. %C A083811 1. a(n) = 36 + 360 + 3600+ ...+ up to n terms. a(n) = sum of n terms of the geometric progression with the first term 36 and common ratio 10. 2. a(n) = 36*A000042(n).( the unary sequence). %F A083811 a(n) = 4*(10^n - 1). %e A083811 36 + 1 = 37, 2*36 + 1 = 73. %Y A083811 Cf. A000042. %K A083811 base,nonn %O A083811 1,1 %A A083811 _Amarnath Murthy_ and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 08 2003