OFFSET
0,1
COMMENTS
Also known as Cunningham chains of length n of the first kind.
For each positive integer n, is there some integer with Sophie Germain degree of n?
LINKS
Warut Roonguthai, Yves Gallot's Proth.exe and Cunningham Chains
EXAMPLE
Using f(x)=2x+1, 11 -> 23 -> 47 -> 95, which is composite; thus a(3)=11.
MATHEMATICA
NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; f[n_] := Block[{k = 2}, While[ Length[ NestWhileList[2# + 1 &, k, PrimeQ]] != n + 1, k = NextPrim[k]]; k]; Table[f[n], {n, 1, 8}]
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Reiner Martin, Jul 14 2001
EXTENSIONS
More terms from Jud McCranie, Jul 20 2001
Edited and extended by Robert G. Wilson v, Nov 21 2002
STATUS
approved