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 A163331 #15 Jul 06 2025 14:58:03 %S A163331 0,2,5,1,4,8,3,7,12,9,14,20,13,19,26,18,25,33,27,35,44,34,43,53,42,52, %T A163331 63,6,11,17,10,16,23,15,22,30,24,32,41,31,40,50,39,49,60,51,62,74,61, %U A163331 73,86,72,85,99,21,29,38,28,37,47,36,46,57,48,59,71,58,70,83,69,82,96 %N A163331 Inverse permutation to A163330. %H A163331 Antti Karttunen, <a href="/A163331/b163331.txt">Table of n, a(n) for n = 0..6560</a> %H A163331 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A163331 a(n) = A001477bi(A163326(n),A163325(n)), where A001477bi(x,y) = (((x+y)^2)+x+(3y))/2. %o A163331 (Scheme) (define (A163331 n) (A001477bi (A163326 n) (A163325 n))) %o A163331 (define (A001477bi x y) (/ (+ (expt (+ x y) 2) x (* 3 y)) 2)) %Y A163331 Inverse: A163330. a(n) = A163329(A163327(n)). Cf. A007089. %K A163331 nonn,base %O A163331 0,2 %A A163331 _Antti Karttunen_, Jul 29 2009