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A198694
a(n) = 7*4^n-1.
3
6, 27, 111, 447, 1791, 7167, 28671, 114687, 458751, 1835007, 7340031, 29360127, 117440511, 469762047, 1879048191, 7516192767, 30064771071, 120259084287, 481036337151, 1924145348607, 7696581394431, 30786325577727, 123145302310911, 492581209243647, 1970324836974591
OFFSET
0,1
FORMULA
a(n) = 4*a(n-1)+3.
a(n) = 5*a(n-1)-4*a(n-2), n>1.
G.f.: ( 6-3*x ) / ( (4*x-1)*(x-1) ). - R. J. Mathar, Oct 30 2011
E.g.f.: exp(x)*(7*exp(3*x) - 1). - Stefano Spezia, Apr 17 2024
MATHEMATICA
7*4^Range[0, 30]-1 (* or *) LinearRecurrence[{5, -4}, {6, 27}, 30] (* Harvey P. Dale, Nov 14 2018 *)
PROG
(Magma) [7*4^n-1: n in [0..30]]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Oct 29 2011
STATUS
approved