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 A131392 #2 Mar 30 2012 18:57:10 %S A131392 3,6,7,9,12,14,15,18,20,22,23,26,27,30,31,34,36,38,40,42,43,45,48,50, %T A131392 52,54,55,58,60,62,64,66,67,70,71,74,76,78,80,82,84,86,87,89,91,93,96, %U A131392 98,100,102,104,106,107,110,112,114,116,118,120,122,124,126,128,131,132 %N A131392 Positions of negative integers in A131389, minus 1. %C A131392 If A131389 is a permutation of the integers, as conjectured, then A131392 is the complement of A131391. %F A131392 a(n) = -1 + position of the n-th negative integer in the sequence A131389=(0,1,2,-1,3,4,-2,-3,6,-4,5,...) %e A131392 The 5th negative integer to occur in A131391 is -5, which occurs in position 13, so that a(5)=13-1=12. %Y A131392 Cf. A131388, A131389, A131390, A131391, A131393, A131394, A131395, A131396, A131397. %K A131392 nonn %O A131392 1,1 %A A131392 _Clark Kimberling_, Jul 06 2007