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 A269380 #6 Mar 03 2016 22:50:47 %S A269380 1,1,2,1,3,2,5,1,4,3,7,2,11,5,6,1,13,4,9,3,8,7,17,2,23,11,10,5,25,6, %T A269380 19,1,12,13,15,4,29,9,14,3,37,8,41,7,16,17,43,2,21,23,18,11,47,10,31, %U A269380 5,20,25,35,6,53,19,22,1,27,12,61,13,24,15,67,4,55,29,26,9,71,14,33,3,28,37,77,8,49,41,30,7,83,16,89,17,32,43,39,2 %N A269380 a(1) = 1, after which, for odd numbers: a(n) = A260739(n)-th number k for which A260738(k) = A260738(n)-1, and for even numbers: a(n) = a(n/2). %C A269380 For odd numbers n > 1, a(n) tells which term is on the immediately preceding row of A255127 (square array generated by Ludic sieve), in the same column where n itself is. %H A269380 Antti Karttunen, <a href="/A269380/b269380.txt">Table of n, a(n) for n = 1..33011</a> %F A269380 a(1) = 1; after which, for even numbers a(n) = a(n/2), and for odd numbers a(n) = A255127(A260738(n)-1, A260739(n)). %F A269380 Other identities. For all n >= 1: %F A269380 a(A269379(n)) = n. %o A269380 (definec (A269380 n) (cond ((= 1 n) n) ((even? n) (A269380 (/ n 2))) (else (A255127bi (- (A260738 n) 1) (A260739 n))))) ;; Code for A255127bi given in A255127. %Y A269380 Cf. A255127, A260738, A260739. %Y A269380 Cf. A269172, A269355, A269357, A269382, A269386, A269388 (sequences that use this function). %Y A269380 Cf. also A268674, A269370. %K A269380 nonn %O A269380 1,3 %A A269380 _Antti Karttunen_, Mar 01 2016