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A168212 a(n) = 7*n - a(n-1) + 1 with n>1, a(1)=4. 3
4, 11, 11, 18, 18, 25, 25, 32, 32, 39, 39, 46, 46, 53, 53, 60, 60, 67, 67, 74, 74, 81, 81, 88, 88, 95, 95, 102, 102, 109, 109, 116, 116, 123, 123, 130, 130, 137, 137, 144, 144, 151, 151, 158, 158, 165, 165, 172, 172, 179, 179, 186, 186, 193, 193, 200, 200, 207, 207 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

From R. J. Mathar, Nov 22 2009: (Start)

a(n) = a(n-1) +a(n-2) -a(n-3).

a(n) = (9 + 14*n + 7*(-1)^n)/4.

G.f.: x*(4 + 7*x - 4*x^2)/((1+x)* (x-1)^2). (End)

E.g.f.: (1/4)*(7 - 16*exp(x) + (9 + 14*x)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 15 2016

MATHEMATICA

LinearRecurrence[{1, 1, -1}, {4, 11, 11}, 60] (* Vincenzo Librandi, Feb 28 2012 *)

PROG

(MAGMA) I:=[4, 11, 11]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..40]]; // Vincenzo Librandi, Feb 28 2012

CROSSREFS

Sequence in context: A222284 A020949 A210693 * A014449 A281387 A098060

Adjacent sequences:  A168209 A168210 A168211 * A168213 A168214 A168215

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 20 2009

STATUS

approved

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Last modified March 30 18:30 EDT 2017. Contains 284302 sequences.