A198915 a(n) = 1 - 2^k + 4^k where k = 3^n.
3, 57, 261633, 18014398375264257, 5846006549323611672814736913013492849365380759553
Offset: 0
Links
- Vincenzo Librandi, Table of n, a(n) for n = 0..6
- Dario A. Alpern, Factors of Generalized Fermat Numbers
Crossrefs
Cf. A051154.
Programs
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Magma
[4^(3^n) - 2^(3^n) + 1: n in [0..7]]; // Vincenzo Librandi, Jun 29 2014
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Maple
A198915:=n->4^(3^n) - 2^(3^n) + 1: seq(A198915(n), n=0..6); # Wesley Ivan Hurt, May 03 2017
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Mathematica
Table[4^(3^n) - 2^(3^n) + 1, {n, 0, 5}] -
PARI
a(n)=1<<(2*3^n)-1<<3^n+1 \\ Charles R Greathouse IV, Oct 31 2011