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A198080 a(n)=(3^(3n+3)- 26n - 27)/169. 1
0, 4, 116, 3144, 84904, 2292428, 61895580, 1671180688, 45121878608, 1218290722452, 32893849506244, 888133936668632, 23979616290053112, 647449639831434076, 17481140275448720108, 471990787437115442976, 12743751260802116960416, 344081284041657157931300 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Second differences are four times the entries of A009971. - R. J. Mathar, Oct 25 2011

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..700

Index entries for linear recurrences with constant coefficients, signature (29,-55,27).

FORMULA

a(n) = (3^(3*n+3) - 26*n - 27)/169.

G.f. -4*x / ( (27*x-1)*(x-1)^2 ). - R. J. Mathar, Oct 25 2011

EXAMPLE

a(1) = (3^(3+3)-26-27)/169=676/169 = 4.

MAPLE

for n from 0 to 30 do:x:=(3^(3*n+3) - 26*n - 27)/169  :  printf(`%d, `, x):od:

MATHEMATICA

LinearRecurrence[{29, -55, 27}, {0, 4, 116}, 50] (* Vincenzo Librandi, Nov 25 2011 *)

PROG

(MAGMA) I:=[0, 4, 116]; [n le 3 select I[n] else 29*Self(n-1)-55*Self(n-2)+27*Self(n-3): n in [1..20]]; // Vincenzo Librandi, Nov 25 2011

(PARI) a(n)=(3^(3*n+3)-26*n-27)/169 \\ Charles R Greathouse IV, Jul 06 2017

CROSSREFS

Sequence in context: A261457 A080482 A206689 * A272158 A194535 A030255

Adjacent sequences:  A198077 A198078 A198079 * A198081 A198082 A198083

KEYWORD

nonn,easy

AUTHOR

Michel Lagneau, Oct 24 2011

STATUS

approved

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Last modified November 20 12:20 EST 2017. Contains 294968 sequences.