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 A257504 #7 May 06 2015 21:44:14 %S A257504 1,2,4,3,7,11,16,22,29,37,46,5,56,67,79,8,92,6,106,121,137,12,154,172, %T A257504 191,211,232,254,277,301,326,352,379,407,436,466,497,529,562,596,631, %U A257504 667,704,742,781,821,862,17,904,947,991,23,1036,1082,1129,1177,1226,1276,1327,30,1379,1432,1486,38,1541,47,1597,1654,1712,57,1771,9 %N A257504 Inverse permutation to A257503. %H A257504 Antti Karttunen, <a href="/A257504/b257504.txt">Table of n, a(n) for n = 1..10440</a> %H A257504 <a href="/index/Fa#facbase">Index entries for sequences related to factorial base representation</a> %H A257504 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A257504 a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where c = A257681(n), and r = A257679(n). %o A257504 (Scheme) (define (A257504 n) (let ((col (A257681 n)) (row (A257679 n))) (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2)))) %Y A257504 Inverse: A257503. %Y A257504 Cf. A257679, A257681. %K A257504 nonn %O A257504 1,2 %A A257504 _Antti Karttunen_, May 06 2015