A168563 a(n) = (n-th prime > 3) minus (n-th composite number).

1, 1, 3, 4, 7, 7, 9, 14, 15, 19, 21, 22, 25, 29, 34, 35, 40, 43, 43, 47, 50, 55, 62, 65, 65, 68, 69, 71, 83, 86, 91, 91, 100, 101, 106, 111, 113, 118, 123, 124, 133, 133, 135, 136, 147, 158, 161, 161, 164, 169, 169, 177, 182, 187, 192, 193, 197, 200, 201, 209, 222, 225, 226

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 29 2009

Keywords

• nonn
• easy

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A161671.

Programs

Mathematica

Module[{nn=100,pr,cmp},cmp=Select[Range[nn],CompositeQ];pr=Prime[ Range[ 3, Length[cmp]+2]];pr-cmp] (* Harvey P. Dale, May 28 2015 *)

Formula

a(n) = prime(n+2)-composite(n) = A161671(n+2).

Extensions

Edited by Charles R Greathouse IV, Mar 25 2010