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A330825 Numbers of the form 2^(2^n)*F_n, where F_n is a Fermat prime, A019434. 1
6, 20, 272, 65792, 4295032832 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers with power-spectral basis {F_n,(F_n-1)^2}.  The first element of the power-spectral 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

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Last modified August 10 01:45 EDT 2020. Contains 336363 sequences. (Running on oeis4.)