A164029 a(n) = nonprime(n) + (-1)^(nonprime(n)).

1, 0, 5, 7, 9, 8, 11, 13, 15, 14, 17, 19, 21, 20, 23, 25, 24, 27, 26, 29, 31, 33, 32, 35, 34, 37, 39, 38, 41, 43, 45, 44, 47, 49, 48, 51, 50, 53, 55, 54, 57, 56, 59, 61, 63, 62, 65, 64, 67, 69, 68, 71, 73, 75, 74, 77, 76, 79, 81, 80, 83, 85, 84, 87, 86, 89, 91, 90, 93, 92, 95

Offset

1,3

Links

G. C. Greubel, Table of n, a(n) for n = 1..5000

Formula

a(n) = A141468(n) + (-1)^A141468(n).

Example

a(1)=0+(-1)^0=1. a(2)=1+(-1)^1=0. a(3)=4+(-1)^4=5.

Maple

A141468 := proc(n) option remember ; local a; if n <= 2 then n-1 ; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; fi; od: fi; end:
A164029 := proc(n) A141468(n)+(-1)^A141468(n) ; end: seq(A164029(n), n=1..80) ; # R. J. Mathar, Aug 11 2009

Mathematica

Join[{1}, With[{nn=100}, #+(-1)^#&/@Complement[Range[nn], Prime[ Range[ PrimePi[nn]]]]]] (* Harvey P. Dale, Jul 24 2011 *)

Crossrefs

Cf. A141468.

Sequence in context: A228578 A242742 A323602 * A364681 A143730 A354454

Adjacent sequences: A164026 A164027 A164028 * A164030 A164031 A164032

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Aug 08 2009

Extensions

a(58) corrected by R. J. Mathar, Aug 11 2009

Status

approved