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 A255567 #25 May 30 2016 18:23:09 %S A255567 1,2,3,12,13,16,17,72,73,76,77,90,91,94,95,480,481,484,485,498,499, %T A255567 502,503,576,577,580,581,594,595,598,599,3600,3601,3604,3605,3618, %U A255567 3619,3622,3623,3696,3697,3700,3701,3714,3715,3718,3719,4200,4201,4204,4205,4218,4219,4222,4223,4296,4297,4300,4301,4314,4315,4318,4319 %N A255567 a(1) = 1, a(2) = 2, after which, a(2n+1) = 1 + a(2n), a(2n) = A255411(a(n)). %C A255567 From 2 onward, the sequence seems to give those n for which A256450(A255411(n))+1 = A255411(A256450(n)), i.e., grandparents for those cousins in tree A255566 where the cousin at the right side is one more than the cousin at the left side. %H A255567 Antti Karttunen, <a href="/A255567/b255567.txt">Table of n, a(n) for n = 1..1023</a> %F A255567 a(1) = 1, a(2) = 2, after which, a(2n+1) = 1 + a(2n), a(2n) = A255411(a(n)). %e A255567 This sequence can be represented as a binary tree. Apart from the 1 at root, and its children 2 and 3, from then on each left hand child is produced as A255411(n), and each right hand child as 1 + A255411(n) when parent contains n >= 2: %e A255567 ..................1.................. %e A255567 2 3 %e A255567 12......./ \.......13 16......./ \.......17 %e A255567 / \ / \ / \ / \ %e A255567 / \ / \ / \ / \ %e A255567 / \ / \ / \ / \ %e A255567 72 73 76 77 90 91 94 95 %e A255567 480 481 484 485 498 499 502 503 576 577 580 581 594 595 598 599 %e A255567 etc. %o A255567 (Scheme, with _Antti Karttunen_'s IntSeq-library) %o A255567 (definec (A255567 n) (cond ((<= n 2) n) ((odd? n) (+ 1 (A255567 (- n 1)))) (else (A255411 (A255567 (/ n 2)))))) %o A255567 ;; This for now conjectured to be equal from a(2) onward: %o A255567 (define A255567 (MATCHING-POS 2 1 (lambda (n) (= (+ 1 (A256450 (A255411 n))) (A255411 (A256450 n)))))) %Y A255567 Cf. A256450, A255411. See also the tree illustration in A255566. %K A255567 nonn %O A255567 1,2 %A A255567 _Antti Karttunen_, May 05 2015 %E A255567 Edited because of the changed starting offset of A256450 - _Antti Karttunen_, May 30 2016