This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

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