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 A269857 #9 Dec 13 2023 08:23:02 %S A269857 1,2,3,4,5,6,9,8,10,12,7,18,15,16,20,24,25,14,21,36,30,32,27,40,48,50, %T A269857 28,42,33,72,11,60,64,54,80,96,51,100,56,84,35,66,45,144,22,120,57, %U A269857 128,108,160,192,102,69,200,112,168,70,132,49,90,39,288,44,240,114,256,55,216,320,384,105,204,87,138,400 %N A269857 Permutation of natural numbers: a(1) = 1; if n is an odd prime, a(n) = A250469(a(A026233(n))), else a(n) = 2*(a(A026233(n))). %H A269857 Antti Karttunen, <a href="/A269857/b269857.txt">Table of n, a(n) for n = 1..2662</a> %H A269857 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A269857 a(1) = 1; if n is an odd prime, a(n) = A250469(a(A026233(n))), else a(n) = 2*(a(A026233(n))). %F A269857 As a composition of other permutations: %F A269857 a(n) = A252755(A071574(n)). %o A269857 (Scheme, with memoization-macro definec) %o A269857 (definec (A269857 n) (cond ((<= n 1) n) ((and (odd? n) (= 1 (A010051 n))) (A250469 (A269857 (A026233 n)))) (else (A005843 (A269857 (A026233 n)))))) %Y A269857 Inverse: A269858. %Y A269857 Cf. A005843, A026233, A010051, A250469. %Y A269857 Related or similar permutations: A071574, A252755, A269847. %Y A269857 Differs from A269847 for the first time at n=19, where a(19)=21, while A269847(19)=27. %K A269857 nonn %O A269857 1,2 %A A269857 _Antti Karttunen_, Mar 06 2016