A102885 Index of n in the primes A000040 or nonprimes A141468.

1, 2, 1, 2, 3, 3, 4, 4, 5, 6, 7, 5, 8, 6, 9, 10, 11, 7, 12, 8, 13, 14, 15, 9, 16, 17, 18, 19, 20, 10, 21, 11, 22, 23, 24, 25, 26, 12, 27, 28, 29, 13, 30, 14, 31, 32, 33, 15, 34, 35, 36, 37, 38, 16, 39, 40, 41, 42, 43, 17, 44, 18, 45, 46, 47, 48, 49, 19, 50, 51, 52, 20, 53, 21, 54

Offset: 0

Author

Juri-Stepan Gerasimov, Aug 17 2008

Keywords

• nonn
• easy

Comments

The nonnegative numbers n occur exactly once in either A000040 or A141468. The sequence lists the corresponding index. It is a permutation of A008619.

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A141468, A000040, A026233.

Programs

Mathematica

Module[{nn=80,pr,np},pr=Prime[Range[PrimePi[nn]]];np=Complement[ Range[ 0,nn],pr];Table[If[PrimeQ[n],Position[pr,n],Position[np,n]],{n,0,nn}]]//Flatten (* Harvey P. Dale, Sep 10 2022 *)

Formula

A141468(a(n))=n or A000040(a(n))=n.

Extensions

Edited by R. J. Mathar, Aug 19 2008