A217122 a(n) = (number of 1's in binary expansion of n)th positive number not among the previous terms

1, 2, 4, 3, 6, 7, 9, 5, 10, 11, 13, 12, 15, 16, 18, 8, 17, 19, 21, 20, 23, 24, 26, 22, 27, 28, 30, 29, 32, 33, 35, 14, 31, 34, 37, 36, 39, 40, 42, 38, 43, 44, 46, 45, 48, 49, 51, 41, 50, 52, 54, 53, 56, 57, 59, 55, 60, 61, 63, 62, 65, 66, 68, 25, 58, 64, 69, 67, 71, 72, 74, 70, 75, 76, 78, 77, 80, 81, 83, 73, 82, 84, 86, 85, 88, 89, 91, 87, 92

Offset

1,2

Comments

This is a permutation of the positive numbers.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Index entries for sequences that are permutations of the natural numbers

Example

3 has 2 1's in its binary expansion, and the 2nd positive number not among the previous terms is 4; hence a(3)=4

Prog

(Haskell)
import Data.List (delete)
a217122 n = a217122_list !! (n-1)
a217122_list = f 1 [0..] where
   f x zs = y : f (x + 1) (delete y zs) where
     y = zs !! a000120 x
-- Reinhard Zumkeller, May 11 2013

Crossrefs

Cf. A000120: number of 1's in binary expansion of n.

Cf. A225589 (inverse), A075311.

Sequence in context: A358467 A006016 A227413 * A239622 A245604 A054239

Adjacent sequences: A217119 A217120 A217121 * A217123 A217124 A217125

Keyword

nonn,base

Author

Paul Tek, Mar 16 2013

Status

approved