cp's OEIS Frontend

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.

A266150 Take the binary representation of n, increase each run of 0's by one 0 if the length of run is odd, otherwise, if length of run is even, remove one 0. a(n) is the decimal equivalent of the result.

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%I A266150 #14 Jan 20 2019 23:18:55
%S A266150 0,1,4,3,2,9,12,7,16,5,36,19,6,25,28,15,8,33,20,11,18,73,76,39,48,13,
%T A266150 100,51,14,57,60,31,64,17,132,67,10,41,44,23,144,37,292,147,38,153,
%U A266150 156,79,24,97,52,27,50,201,204,103,112,29,228,115,30,121,124,63,32
%N A266150 Take the binary representation of n, increase each run of 0's by one 0 if the length of run is odd, otherwise, if length of run is even, remove one 0. a(n) is the decimal equivalent of the result.
%C A266150 This is a self-inverse permutation of the positive integers.
%H A266150 Rémy Sigrist, <a href="/A266150/b266150.txt">Table of n, a(n) for n = 0..8192</a>
%H A266150 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%e A266150 a(4) = 2 since 4 = 100 binary -> 10 = 2 decimal.
%e A266150 a(5) = 9 since 5 = 101 binary -> 1001 = 9 decimal.
%e A266150 a(6) = 12 since 6 = 110 binary -> 1100 = 12 decimal.
%t A266150 Table[FromDigits[#, 2] &@ Flatten[If[First@ # == 0, If[OddQ@ Length@ #, Append[IntegerDigits@ #, 0], Most@ IntegerDigits@ #], #] & /@ Split@ IntegerDigits[n, 2]], {n, 64}] (* _Michael De Vlieger_, Dec 22 2015 *)
%o A266150 (PARI) a(n) = if (n==0, 0, my (b=n%2, r=valuation(n+b, 2), rr=if (b, r, r%2, r+1, r-1)); (a(n\2^r)+b)*2^rr-b) \\ _Rémy Sigrist_, Jan 20 2019
%Y A266150 Cf. A007088, A084483, A162853, A175046, A175047, A175048, A266151.
%K A266150 nonn,base
%O A266150 0,3
%A A266150 _Alex Ratushnyak_, Dec 21 2015
%E A266150 a(0) = 0 prepended by _Rémy Sigrist_, Jan 20 2019