A152580 a(n) = 7^(2^n) + 2.

9, 51, 2403, 5764803, 33232930569603, 1104427674243920646305299203

Offset

0,1

Comments

These numbers are divisible by 3. This follows by expanding the binomial (6+1)^(2^n) + 2 to get 6h + 1 + 2 for some h. Therefore 3 divides 7^(2^n) + 2.

Links

Table of n, a(n) for n=0..5.

Formula

a(n) = A165425(n+3) + 2. - R. J. Mathar, Sep 10 2016

Maple

A152580:=n->7^(2^n) + 2: seq(A152580(n), n=0..8); # Wesley Ivan Hurt, Jan 22 2017

Prog

(PARI) g(a, n) = if(a%2, b=2, b=1); for(x=0, n, y=a^(2^x)+b; print1(y", "))
(PARI) a(n) = 7^(2^n) + 2; \\ Michel Marcus, Jan 24 2017

Crossrefs

Cf. A165425.

Sequence in context: A272393 A231748 A181161 * A197722 A172470 A120665

Adjacent sequences: A152577 A152578 A152579 * A152581 A152582 A152583

Keyword

nonn,easy

Author

Cino Hilliard, Dec 08 2008

Status

approved