OFFSET
1,1
COMMENTS
Idea resulted from seqfan posts by Artur Jasinski.
FORMULA
a(n)=16^n - 3*2^(2*n - 1) - 1=(2^(2*n - 1) - 1)*(2^(2*n + 1) + 1).
MATHEMATICA
b[n_] := 16^n - 3*2^(2*n - 1) - 1. Table[b[n], {n, 1, 30}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Roger L. Bagula, Nov 24 2008
EXTENSIONS
Definition corrected by N. J. A. Sloane, Dec 22 2009 (these are not semiprimes).
STATUS
approved