A063378 Smallest number whose Sophie Germain degree (see A063377) is n.

4, 7, 3, 11, 5, 2, 89, 1122659, 19099919, 85864769, 26089808579, 665043081119, 554688278429, 4090932431513069, 95405042230542329

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

Table of n, a(n) for n=0..14.

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

Cf. A005384, A063377.

Sequence in context: A100127 A130204 A021215 * A280547 A301930 A365940

Adjacent sequences: A063375 A063376 A063377 * A063379 A063380 A063381

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