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URL: https://oeis.org/A168565

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A168565
Let p = prime(n); then a(n) = p + (p-1)/2.
1
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
2,1
COMMENTS
Also numbers k such that (2*k + 1)/3 is prime. - Vicente Izquierdo Gomez, Dec 30 2012
FORMULA
a(n) = (3*prime(n)-1)/2.
EXAMPLE
3+2/2=4, 5+4/2=7, 7+6/2=10, 11+10/2=16,..
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 *)
CROSSREFS
Cf. A162939.
Sequence in context: A359274 A177965 A179209 * A310711 A115288 A310712
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Edited by N. J. A. Sloane, Jan 04 2013
STATUS
approved