A168565 Let p = prime(n); then a(n) = p + (p-1)/2.

4, 7, 10, 16, 19, 25, 28, 34, 43, 46, 55, 61, 64, 70, 79, 88, 91, 100, 106, 109, 118, 124, 133, 145, 151, 154, 160, 163, 169, 190, 196, 205, 208, 223, 226, 235, 244, 250, 259, 268, 271, 286, 289, 295, 298, 316, 334, 340, 343, 349, 358, 361, 376, 385, 394, 403

Offset: 2

Author

Vladimir Joseph Stephan Orlovsky, Nov 30 2009

Keywords

• nonn

Comments

Also numbers n such that (2n + 1)/3 is prime. - Vicente Izquierdo Gomez, Dec 30 2012

Examples

			3+2/2=4, 5+4/2=7, 7+6/2=10, 11+10/2=16,..
		

Crossrefs

Cf. A162939.

Programs

Mathematica

f[n_]:=n/2; lst={};Do[p=Prime[n];AppendTo[lst,p+f[p-1]],{n,2,5!}];lst
#+(#-1)/2&/@Prime[Range[2,60]] (* Harvey P. Dale, Nov 04 2017 *)

Formula

a(n) = (3*prime(n)-1)/2.

Extensions

Edited by N. J. A. Sloane, Jan 04 2013