A112879 Define a(0)=3; then a(n)=k*a(n-1)^2-1=least prime first of twin primes.

3, 107, 206081, 20894934252011

Offset

0,1

Comments

k sequence in A112880

Links

Table of n, a(n) for n=0..3.

Example

12*3^2-1=107, 107 and 109 twin primes so a(1)=107
18*107^2-1=206081, 206081 and 206083 twin primes so a(2)=206081
a(3)=492*(18*(12*3^2-1)^2-1)^2-1
a(4)=702*(492*(18*(12*3^2-1)^2-1)^2-1)^2-1
a(5)=2310*(702*(492*(18*(12*3^2-1)^2-1)^2-1)^2-1)^2-1
a(6)=2370*(2310*(702*(492*(18*(12*3^2-1)^2-1)^2-1)^2-1)^2-1)^2-1
a(7)=130650*(2370*(2310*(702*(492*(18*(12*3^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1
a(8)=980910*(130650*(2370*(2310*(702*(492*(18*(12*3^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1
a(9)=5528418*(980910*(130650*(2370*(2310*(702*(492*(18*(12*3^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1
a(10)=21357012*(5528418*(980910*(130650*(2370*(2310*(702*(492*(18*(12*3^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1

Crossrefs

Cf. A112880.

Sequence in context: A061308 A302060 A336438 * A172271 A368623 A053861

Adjacent sequences: A112876 A112877 A112878 * A112880 A112881 A112882

Keyword

hard,nonn

Author

Pierre CAMI, Oct 01 2005

Status

approved