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 A071660 #5 Apr 30 2014 01:53:48 %S A071660 0,1,3,2,6,8,7,4,5,15,14,19,20,22,16,21,17,9,10,18,11,12,13,39,41,40, %T A071660 37,38,52,51,53,55,54,60,61,62,64,43,42,56,57,63,44,58,45,23,24,46,25, %U A071660 26,27,47,59,48,28,29,49,30,31,32,50,33,34,35,36,113,112,117,118,120 %N A071660 Permutation of natural numbers induced by the automorphism robl_car_cdr! acting on the parenthesizations encoded by A014486. %H A071660 A. Karttunen, <a href="http://www.iki.fi/~kartturi/matikka/Nekomorphisms/gatomorf.htm">Gatomorphisms</a> (Includes the complete Scheme source for computing this sequence) %H A071660 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %o A071660 (Scheme function implementing this automorphism on list-structures:) %o A071660 (define (robl_car_cdr! s) (cond ((not (pair? s))) ((not (pair? (cdr s))) (swap! s)) (else (robl! s) (robl_car_cdr! (car s)) (robl_car_cdr! (cdr s)))) s) %o A071660 (define (robl! s) (let ((ex-car (car s))) (set-car! s (cddr s)) (set-cdr! (cdr s) ex-car) (swap! (cdr s)) (swap! s) s)) %o A071660 (define (swap! s) (let ((ex-car (car s))) (set-car! s (cdr s)) (set-cdr! s ex-car) s)) %Y A071660 Inverse permutation: A071659. The car/cdr-flipped conjugate of A071655, i.e. A071660(n) = A057163(A071655(A057163(n))). Cf. also A071657, A071658. %K A071660 nonn %O A071660 0,3 %A A071660 _Antti Karttunen_, May 30 2002