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 A125217 #9 Jul 13 2013 12:03:27 %S A125217 2,5,8,11,12,14,17,19,20,23,29,30,32,33,35,38,40,44,50,52,53,54,59,61, %T A125217 62,63,65,75,77,80,82,83,85,90,92,95,98,103,104,109,113,117,118,119, %U A125217 122,124,125,129,132,134,137,138,143,145,147,149,151,158,159,162,164,167 %N A125217 Numbers that can be written uniquely as 4*x*y-x-y with 1<=x<=y. %C A125217 A125203(a(n)) = 1. %C A125217 A124934 is the union of this sequence and A125218. %H A125217 Reinhard Zumkeller, <a href="/A125217/b125217.txt">Table of n, a(n) for n = 1..10000</a> %o A125217 (Haskell) %o A125217 import Data.List (elemIndices) %o A125217 a125217 n = a125217_list !! (n-1) %o A125217 a125217_list = map (+ 1) $ elemIndices 1 a125203_list %o A125217 -- _Reinhard Zumkeller_, Jan 02 2013 %K A125217 nonn %O A125217 1,1 %A A125217 _Reinhard Zumkeller_, Nov 24 2006