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A168613
a(n) = 3^n - 5.
4
-4, -2, 4, 22, 76, 238, 724, 2182, 6556, 19678, 59044, 177142, 531436, 1594318, 4782964, 14348902, 43046716, 129140158, 387420484, 1162261462, 3486784396, 10460353198, 31381059604, 94143178822, 282429536476, 847288609438
OFFSET
0,1
FORMULA
a(n) = 3*a(n-1) + 10 with a(0)=-4.
G.f.: 2*(7*x - 2)/((1-x)*(1-3*x)). - Vincenzo Librandi, Jul 06 2012
a(n) = 4*a(n-1) - 3*a(n-2). - Vincenzo Librandi, Jul 06 2012
a(n) = 2*A116970(n) + 2 with A116970(0)=-3, A116970(1)=-2. - Bruno Berselli, Jul 06 2012
E.g.f.: exp(3*x) - 5*exp(x). - G. C. Greubel, Jul 27 2016
MATHEMATICA
CoefficientList[Series[2*(7*x-2)/((1-x)*(1-3*x)), {x, 0, 40}], x] (* Vincenzo Librandi, Jul 06 2012 *)
LinearRecurrence[{4, -3}, {-4, -2}, 25] (* G. C. Greubel, Jul 27 2016 *)
3^Range[0, 30]-5 (* Harvey P. Dale, Sep 12 2022 *)
PROG
(Magma) I:=[-4, -2]; [n le 2 select I[n] else 4*Self(n-1)-3*Self(n-2): n in [1..30]]; // Vincenzo Librandi, Jul 06 2012
CROSSREFS
Cf. A168610.
Sequence in context: A134434 A349184 A261254 * A248251 A139809 A348640
KEYWORD
sign,easy
AUTHOR
Vincenzo Librandi, Dec 01 2009
EXTENSIONS
Formula and examples edited to use correct offset by Jon E. Schoenfield, Jun 19 2010
STATUS
approved