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 A277883 #5 Nov 05 2016 07:27:01 %S A277883 1,2,3,4,5,6,7,11,8,9,16,10,22,29,12,37,17,13,46,14,56,67,23,15,79,92, %T A277883 30,106,38,18,121,137,47,24,154,19,172,191,57,20,211,232,68,254,80,31, %U A277883 277,21,301,326,93,352,107,39,379,407,122,48,436,25,466,497,138,529,155,58,562,32,596,631,173,26,667,704,192,742,212,69,781,27 %N A277883 Inverse permutation to A277882. %H A277883 Antti Karttunen, <a href="/A277883/b277883.txt">Table of n, a(n) for n = 1..8192</a> %H A277883 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A277883 a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where c = A277813(n), and r = A277822(n). %o A277883 (Scheme) (define (A277883 n) (let ((col (A277813 n)) (row (A277822 n))) (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2)))) %Y A277883 Inverse: A277882. %Y A277883 Cf. A277813, A277822. %K A277883 nonn %O A277883 1,2 %A A277883 _Antti Karttunen_, Nov 03 2016