OFFSET
1,3
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
a(5) is the smallest nonprime > 2*a(4)=2*9=18, hence a(5)=20.
MATHEMATICA
np[n_]:=Module[{k=2n+1}, If[PrimeQ[k], k+1, k]]; NestList[np, 0, 40] (* Harvey P. Dale, May 23 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Feb 08 2009
EXTENSIONS
More terms from R. J. Mathar, Feb 10 2009
STATUS
approved