A330830 Numbers of the form (F_n-2)^2*F_n^2, where F_n is a Fermat prime, A019434. Also the first element of the power-spectral basis of A330829.

9, 225, 65025, 4294836225, 18446744065119617025

Offset

1,1

Comments

The second element of the power-spectral basis of A330829 is A330831. We also have a(n) = (2^(2*2^n)-1)^2.

Links

Table of n, a(n) for n=1..5.

Formula

a(n) = (A019434(n)-2)^2*A019434(n)^2.

Example

a(1) = (3-2)^2*3^2  =9.

Maple

a := proc(n) if isprime(2^(2^n)+1) then return (2^(2*2^n)-1)^2 fi; end;
[seq(a(n), n=0..4)];

Crossrefs

Cf. A000215, A001146, A019434, A330828.

Sequence in context: A095363 A138564 A285985 * A218536 A338377 A211048

Adjacent sequences: A330827 A330828 A330829 * A330831 A330832 A330833

Keyword

nonn,hard

Author

Walter Kehowski, Jan 06 2020

Status

approved