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A226508 a(n) = Sum_{i=3^n..3^(n+1)-1} i. 1
3, 33, 315, 2889, 26163, 235953, 2125035, 19129689, 172180323, 1549662273, 13947078555, 125524061289, 1129717614483, 10167461718993, 91507165036875, 823564514029689, 7412080712360643, 66708726669526113 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Partial sums give 3, 36, 351, 3240, 29403,...: A026121.

LINKS

Table of n, a(n) for n=0..17.

Index entries for linear recurrences with constant coefficients, signature (12,-27).

FORMULA

G.f.: 3*(1-x)/(1-12*x+27*x^2). [Bruno Berselli, Jun 11 2013]

a(n) = 3^(n-1)*(4*3^(n+1)-3). [Bruno Berselli, Jun 11 2013]

a(0)=3, a(1)=33, a(n)=12*a(n-1)-27*a(n-2). - Harvey P. Dale, Jun 19 2013

EXAMPLE

a(0) = 1+2 = 3,

a(1) = 3+4+5+6+7+8 = 33.

MATHEMATICA

Table[3^(n - 1) (4 3^(n + 1) - 3), {n, 0, 20}] (* Bruno Berselli, Jun 11 2013 *)

LinearRecurrence[{12, -27}, {3, 33}, 30] (* Harvey P. Dale, Jun 19 2013 *)

PROG

(PARI) a(n) = sum(i=3^n, 3^(n+1)-1, i) \\ Michel Marcus, Jun 11 2013

CROSSREFS

Cf. A010035, A026121.

Sequence in context: A107127 A207323 A135697 * A097486 A121515 A221883

Adjacent sequences:  A226505 A226506 A226507 * A226509 A226510 A226511

KEYWORD

nonn,easy

AUTHOR

Michel Marcus, Jun 10 2013

STATUS

approved

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Last modified October 19 04:40 EDT 2019. Contains 328211 sequences. (Running on oeis4.)