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A152101
a(n)=16^n - 3*2^(2*n - 1) - 1.
0
9, 231, 3999, 65151, 1047039, 16771071, 268410879, 4294868991, 68719083519, 1099510054911, 17592179752959, 281474951544831, 4503599526707199, 72057593635274751, 1152921502996234239, 18446744067267100671
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
Sequence in context: A295941 A247019 A181205 * A230178 A165389 A153223
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