login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A131051 Row sums of triangle A133805. 9
1, 3, 8, 18, 38, 78, 158, 318, 638, 1278, 2558, 5118, 10238, 20478, 40958, 81918, 163838, 327678, 655358, 1310718, 2621438, 5242878, 10485758, 20971518, 41943038, 83886078, 167772158, 335544318, 671088638, 1342177278, 2684354558 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Last digit of a(n) is 8 for n > 2. - Jon Perry, Nov 19 2012

LINKS

Table of n, a(n) for n=1..31.

FORMULA

Binomial transform of [1, 2, 3, 2, 3, 2, 3, ...].

O.g.f.: (1+x^2)/((1-x)(1-2*x)). a(n)=A051633(n-2). - R. J. Mathar, Jun 13 2008

a(n) = 5*2^(n-2)-2, n>1. - Gary Detlefs, Jun 22 2010

a(n) = 2(n-1) + Sum_{i=1..n-1} a(i). - Jon Perry, Nov 19 2012

EXAMPLE

a(4) = 18 = sum of row 4 terms of triangle A133805: (7 + 6 + 4 + 1).

a(4) = 18 = (1, 3, 3, 1), dot (1, 2, 3, 2) = (1 + 6 + 9 + 2).

PROG

(Magma) a:=[1]; for n in [2..31] do Append(~a, 2*n-2+&+[a[i]:i in [1..n-1]]); end for; a; // Marius A. Burtea, Oct 15 2019

(Magma) R<x>:=PowerSeriesRing(Integers(), 31); Coefficients(R!( (1+x^2)/((1-x)*(1-2*x)))); // Marius A. Burtea, Oct 15 2019

CROSSREFS

Cf. A133805.

Cf. A083329, A053209.

Sequence in context: A006478 A104187 A051633 * A172265 A258272 A117727

Adjacent sequences: A131048 A131049 A131050 * A131052 A131053 A131054

KEYWORD

nonn

AUTHOR

Gary W. Adamson, Sep 23 2007

EXTENSIONS

More terms from R. J. Mathar, Jun 13 2008

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 29 10:31 EST 2022. Contains 358424 sequences. (Running on oeis4.)