A330828 The squares of the Fermat primes, (A019434(n))^2.

9, 25, 289, 66049, 4295098369

Offset: 1

Author

Walter Kehowski, Jan 06 2020

Keywords

• nonn
• hard
• more

Comments

Also the first element of the power-spectral basis of A330826. The second element of the power-spectral basis of A330826 is A001146(n+1), n=0..4.

Examples

			a(1) = 3^2 = 9. The spectral basis of A330826(1) = 12 is {9,4}, consisting of primes and powers.
		

Crossrefs

Cf. A000215, A001146, A019434, A330829.

Programs

Maple

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

Mathematica

(2^2^Select[Range[0,5],PrimeQ[2^(2^#)+1] &]+1)^2 (* Stefano Spezia, May 01 2025 *)

Formula

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