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 A227182 #20 Apr 15 2025 14:57:30 %S A227182 0,1,4,3,2,11,10,9,8,7,6,5,24,23,22,21,20,19,18,17,16,15,14,13,12,45, %T A227182 44,43,42,41,40,39,38,37,36,35,34,33,32,31,30,29,28,27,26,25,76,75,74, %U A227182 73,72,71,70,69,68,67,66,65,64,63,62,61,60,59,58,57,56,55,54,53,52,51,50,49,48,47,46 %N A227182 Simple self-inverse permutation of natural numbers: List each block of n^2 - n + 1 numbers from ((n-1)^3 + 2*(n-1))/3 + 1 to (n^3 + 2*n)/3 in reverse order. %C A227182 In other words, after zero, list each block of A002061(n) numbers from A116731(n) to A006527(n) in reverse order. %H A227182 Antti Karttunen, <a href="/A227182/b227182.txt">Table of n, a(n) for n = 0..9951</a> %H A227182 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A227182 a(n) = A006527(A227177(n)) - A227179(n). %t A227182 Flatten[(Reverse/@( (-1+#) (9-5 #+#^2)/3+Range[(#-2) (#-1)+1]-1)&)[Range[7]]] (* _Peter J. C. Moses_, Jul 11 2013 *) %o A227182 (Scheme) (define (A227182 n) (- (A006527 (A227177 n)) (A227179 n))) %Y A227182 Cf. A227177, A227179, A227147. %K A227182 nonn %O A227182 0,3 %A A227182 _Antti Karttunen_, Jul 04 2013