A171575 n-th noncomposite number plus n-th even nonprime number.

1, 6, 9, 13, 17, 23, 27, 33, 37, 43, 51, 55, 63, 69, 73, 79, 87, 95, 99, 107, 113, 117, 125, 131, 139, 149, 155, 159, 165, 169, 175, 191, 197, 205, 209, 221, 225, 233, 241, 247, 255, 263, 267, 279, 283, 289, 293, 307, 321, 327, 331, 337, 345, 349, 361, 369, 377

Offset: 1

Author

Juri-Stepan Gerasimov, Dec 12 2009

Keywords

• nonn

Examples

			a(1) = 1 + 0 = 1, a(2) = 2 + 4 = 6, a(3) = 3 + 6 = 9.
		

Crossrefs

Cf. A008578(the noncomposite numbers), A163300(the even nonprime numbers).

Programs

Mathematica

Module[{nc=Select[Range[300],!CompositeQ[#]&],len},len=Length[nc];Join[ {1},Rest[Total/@Thread[{nc,Range[2,2len,2]}]]]] (* Harvey P. Dale, Mar 08 2018 *)

Formula

a(n) = A008578(n) + A163300(n).

Extensions

Entries checked by R. J. Mathar, May 23 2010