A350091 a(n) = a(floor(n/4)) for n == 2 (mod 4), otherwise n.

0, 1, 0, 3, 4, 5, 1, 7, 8, 9, 0, 11, 12, 13, 3, 15, 16, 17, 4, 19, 20, 21, 5, 23, 24, 25, 1, 27, 28, 29, 7, 31, 32, 33, 8, 35, 36, 37, 9, 39, 40, 41, 0, 43, 44, 45, 11, 47, 48, 49, 12, 51, 52, 53, 13, 55, 56, 57, 3, 59, 60, 61, 15, 63, 64, 65, 16, 67, 68, 69, 17, 71, 72, 73

Offset

0,4

Comments

a(n) deletes any trailing '10' bit pairs from n. So in base 4, it removes all trailing '2' digits.

Links

Table of n, a(n) for n=0..73.

Formula

A139391(2*a(n)+1) = A139391(2*n+1).

Example

Numbers between '' are in base 2: '0'->'0', so a(0)=0. '110'->'1', so a(6)=1. '1010'->'10' -> '0', so a(10)=0. a(floor((2^1000001)/3))=0.

Mathematica

a[n_] := a[n] = If[Mod[n, 4] == 2, a[(n - 2)/4], n]; Array[a, 100, 0] (* Amiram Eldar, Dec 14 2021 *)

Prog

(PARI) a(n) = if(2!=(n%4), n, my(m=3*n+2); m=m/4^valuation(m, 4); (m+1)/3-1)

Crossrefs

Cf. A006519, A139391, A001511, A065883 (chop trailing 00 bit pairs).

Sequence in context: A051993 A174530 A280490 * A135347 A370116 A345708

Adjacent sequences: A350088 A350089 A350090 * A350092 A350093 A350094

Keyword

nonn,easy

Author

Ruud H.G. van Tol, Dec 14 2021

Status

approved