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A099359
a(n) = (2^n + 1)^3 - 2.
4
6, 25, 123, 727, 4911, 35935, 274623, 2146687, 16974591, 135005695, 1076890623, 8602523647, 68769820671, 549957165055, 4398851866623, 35187593412607, 281487861809151, 2251851353686015, 18014604668698623, 144116012711149567, 1152924803144876031
OFFSET
0,1
LINKS
Eric Weisstein's World of Mathematics, Integer sequence primes.
FORMULA
From Colin Barker, Jan 10 2017: (Start)
a(n) = (3*2^n + 3*4^n + 8^n - 1).
a(n) = 15*a(n-1) - 70*a(n-2) + 120*a(n-3) - 64*a(n-4) for n>3.
G.f.: (6 - 65*x + 168*x^2 - 88*x^3) / ((1 - x)*(1 - 2*x)*(1 - 4*x)*(1 - 8*x)).
(End)
EXAMPLE
(2^1 + 1)^3 - 2 = 25.
MATHEMATICA
Table[(2^n + 1)^3 - 2, {n, 19}] (* Robert G. Wilson v, Nov 23 2004 *)
PROG
(PARI) a(n)=(2^n+1)^3-2 \\ Charles R Greathouse IV, Feb 19 2016
(PARI) Vec((6 - 65*x + 168*x^2 - 88*x^3) / ((1 - x)*(1 - 2*x)*(1 - 4*x)*(1 - 8*x)) + O(x^30)) \\ Colin Barker, Jan 10 2017
CROSSREFS
Cf. A098878.
Sequence in context: A298700 A215763 A153481 * A073967 A188207 A275541
KEYWORD
nonn,easy
AUTHOR
Parthasarathy Nambi, Nov 16 2004
EXTENSIONS
More terms from Robert G. Wilson v, Nov 23 2004
STATUS
approved