

A330825


Numbers of the form 2^(2^n)*F_n, where F_n is a Fermat prime, A019434.


1




OFFSET

1,1


COMMENTS

Also numbers with powerspectral basis {F_n,(F_n1)^2}. The first element of the powerspectral basis of a(n) is A019434, and the second element is A001146.


LINKS

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


FORMULA

a(n) = A001146(n)*A019434(n), n = 0..4.


EXAMPLE

a(2) = 2^2*(2^2+1) = 20, and the spectral basis of 20 is {5,16}, consisting of primes and powers.


MAPLE

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


CROSSREFS

Cf. A000215, A001146, A019434.
Sequence in context: A227769 A309454 A267903 * A280039 A216912 A175671
Adjacent sequences: A330822 A330823 A330824 * A330826 A330827 A330828


KEYWORD

nonn,more


AUTHOR

Walter Kehowski, Jan 06 2020


STATUS

approved



