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 A069774 #5 May 01 2014 02:46:54 %S A069774 0,1,3,2,7,8,4,6,5,17,18,20,21,22,9,10,14,16,19,11,12,15,13,45,46,48, %T A069774 49,50,54,55,57,58,59,61,62,63,64,23,24,25,26,27,37,38,42,44,47,51,53, %U A069774 56,60,28,29,30,31,32,39,40,43,52,33,34,35,41,36,129,130,132,133,134 %N A069774 Permutation of natural numbers induced by the automorphism RoblDownCar_et_SwapInv! acting on the parenthesizations encoded by A014486. %H A069774 A. Karttunen, <a href="http://www.iki.fi/~kartturi/matikka/Nekomorphisms/gatomorf.htm">Gatomorphisms</a> (Includes the complete Scheme program for computing this sequence) %H A069774 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %o A069774 (Scheme function implementing this automorphism on list-structures:) (define (RoblDownCar_et_SwapInv! s) (cond ((not (pair? s))) ((not (pair? (car s))) (swap! s)) (else (RoblDownCar_et_SwapInv! (car s)) (robr! s))) s) %o A069774 (define (robr! s) (let ((ex-cdr (cdr s))) (set-cdr! s (caar s)) (set-car! (car s) ex-cdr) (swap! (car s)) (swap! s) s)) %o A069774 (define (swap! s) (let ((ex-car (car s))) (set-car! s (cdr s)) (set-cdr! s ex-car) s)) %Y A069774 Inverse of A069773, the car/cdr-flipped conjugate of A057502, i.e. A069774(n) = A057163(A057502(A057163(n))). Cf. also A069776. %K A069774 nonn %O A069774 0,3 %A A069774 _Antti Karttunen_, Apr 16 2002