A141819 a(1)=1. a(n) = the smallest integer > a(n-1) that is coprime to the number of 1's in the binary representation of n.

1, 2, 3, 4, 5, 7, 8, 9, 11, 13, 14, 15, 16, 17, 19, 20, 21, 23, 25, 27, 28, 29, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 45, 47, 49, 51, 52, 53, 55, 57, 58, 59, 61, 62, 63, 65, 66, 67, 68, 70, 71, 73, 75, 77, 78, 79, 81, 83, 84, 85, 86, 87, 89, 90, 91, 93, 94, 95, 97, 98, 99, 101, 103

Offset

1,2

Links

Brian Kell, Table of n, a(n) for n=1,...,10000.

Example

19 in binary is 10011, which has 3 ones. a(18) = 23. Checking the integers > 23, 24 is not coprime to 3. But 25 is coprime to 3. So a(19) = 25.

Mathematica

sicp[{n_, a_}]:=Module[{si=a+1, c=DigitCount[n+1, 2, 1]}, While[!CoprimeQ[c, si], si++]; {n+1, si}]; NestList[sicp, {1, 1}, 80][[All, 2]] (* Harvey P. Dale, Jan 06 2019 *)

Crossrefs

Cf. A000120, A141820.

Sequence in context: A229757 A319272 A366142 * A097904 A094387 A050744

Adjacent sequences: A141816 A141817 A141818 * A141820 A141821 A141822

Keyword

nonn

Author

Leroy Quet, Jul 08 2008

Status

approved