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A175976
a(n) = 4^n-3*n+1.
1
2, 2, 11, 56, 245, 1010, 4079, 16364, 65513, 262118, 1048547, 4194272, 16777181, 67108826, 268435415, 1073741780, 4294967249, 17179869134, 68719476683, 274877906888, 1099511627717, 4398046511042, 17592186044351, 70368744177596
OFFSET
0,1
FORMULA
G.f.: ( -2+10*x-17*x^2 ) / ( (4*x-1)*(x-1)^2 ).
From Bruno Berselli, Nov 04 2010: (Start)
a(n)-6*a(n-1)+9*a(n-2)-4*a(n-3) = 0 for n>2.
a(n) = A158879(n)-A131098(n+1) (n>0). (End)
EXAMPLE
a(1)=4-3+1=2. a(2)=16-6+1=11.
MAPLE
A175976 := proc(n) 4^n-3*n+1 ; end proc:
MATHEMATICA
Table[4^n-3n+1, {n, 0, 30}] (* or *) LinearRecurrence[{6, -9, 4}, {2, 2, 11}, 30] (* Harvey P. Dale, Jul 07 2013 *)
PROG
(Magma) [4^n-3*n+1: n in [0..30]]; // Vincenzo Librandi, Mar 20 2014
CROSSREFS
Sequence in context: A184237 A069648 A275869 * A095215 A264712 A217094
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 02 2010
EXTENSIONS
G.f., program and link to recurrences from R. J. Mathar, Nov 03 2010
STATUS
approved