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

Author

Walter Kehowski, Jan 06 2020

Keywords

• nonn
• hard

Comments

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

Examples

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

Crossrefs

Cf. A000215, A001146, A019434, A330828.

Programs

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)];

Formula

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