A105882 Nonprimes of the form r(r(n)+1)+1, where A141468(n)=r(n)=n-th nonprime.

1, 9, 15, 16, 21, 25, 26, 28, 33, 34, 36, 39, 40, 45, 49, 50, 51, 52, 55, 56, 57, 63, 64, 65, 69, 70, 76, 77, 78, 81, 86, 87, 88, 91, 93, 94, 95, 100, 105, 106, 111, 112, 115, 116, 117, 118, 119, 121, 122, 123, 124, 125, 126, 130, 133, 135, 141, 143, 145, 146, 147, 153

Offset: 1

Author

Juri-Stepan Gerasimov, Aug 25 2008

Keywords

• nonn

Examples

			If n=1, then r(r(1)+1)+1=r(0+1)+1=r(1)+1=0+1=1=a(1).
If n=2, then r(r(2)+1)+1=r(1+1)+1=r(2)+1=1+1=2 (prime).
If n=3, then r(r(3)+1)+1=r(4+1)+1=r(5)+1=8+1=9=a(2).
If n=4, then r(r(4)+1)+1=r(6+1)+1=r(7)+1=10+1=11 (prime).
If n=5, then r(r(5)+1)+1=r(8+1)+1=r(9)+1=14+1=15=a(3).
If n=6, then r(r(6)+1)+1=r(9+1)+1=r(10)+1=15+1=16=a(4).
If n=7, then r(r(7)+1)+1=r(10+1)+1=r(11)+1=16+1=17 (prime).
If n=8, then r(r(8)+1)+1=r(12+1)+1=r(13)+1=20+1+21=a(5).
If n=9, then r(r(9)+1)+1=r(14+1)+1=r(15)+1=22+1=23 (prime).
If n=10, then r(r(10)+1)+1=r(15+1)+1=r(16)+1=24+1=25=a(6), etc.
		

Crossrefs

Cf. A000040, A141468.

Extensions

49 and 69 inserted by R. J. Mathar, Sep 05 2008