login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A005010 a(n) = 9*2^n. 30
9, 18, 36, 72, 144, 288, 576, 1152, 2304, 4608, 9216, 18432, 36864, 73728, 147456, 294912, 589824, 1179648, 2359296, 4718592, 9437184, 18874368, 37748736, 75497472, 150994944, 301989888, 603979776, 1207959552, 2415919104 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Row sums of (8, 1)-Pascal triangle A093565. - N. J. A. Sloane, Sep 22 2004

The first differences are the sequence itself. - Alexandre Wajnberg & Eric Angelini, Sep 07 2005

For n>=1, a(n) is equal to the number of functions f:{1,2,...,n+2}->{1,2,3} such that for fixed, different x_1, x_2,...,x_n in {1,2,...,n+2} and fixed y_1, y_2,...,y_n in {1,2,3} we have f(x_i)<>y_i, (i=1,2,...,n). - Milan Janjic, May 10 2007

9 times powers of 2. - Omar E. Pol, Dec 16 2008

a(n) = A173786(n+3,n) for n>2. - Reinhard Zumkeller, Feb 28 2010

Let D(m) = {d(m,i)}, i = 1..q, denote the set of the q divisors of a number m, and consider s0(m) and s1(m) the sums of the divisors that are congruent to 2 and 3 (mod 4) respectively. For n>0, the sequence a(n) lists the numbers m such that s0(m) = 26 and s1(m) = 3. - Michel Lagneau, Feb 10 2017

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..235

Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets

Tanya Khovanova, Recursive Sequences

Index entries for linear recurrences with constant coefficients, signature (2).

FORMULA

a(n) = 9*2^n.

G.f.: 9/(1-2*x).

a(n) = A118416(n+1,5) for n>4. - Reinhard Zumkeller, Apr 27 2006

a(n) = 2*a(n-1), n>0; a(0)=9. - Philippe Deléham, Nov 23 2008

a(n) = 9*A000079(n). - Omar E. Pol, Dec 16 2008

a(n) = 3*A007283(n). - Omar E. Pol, Jul 14 2015

MATHEMATICA

9*2^Range[0, 60] (* Vladimir Joseph Stephan Orlovsky, Jun 09 2011 *)

PROG

(MAGMA) [9*2^n: n in [0..40]]; // Vincenzo Librandi, Apr 28 2011

(PARI) a(n)=9<<n \\ Charles R Greathouse IV, Apr 17 2012

CROSSREFS

Cf. A093565,A173786, A118416, A007283.

Sequence in context: A162689 A033896 A195332 * A245425 A000547 A138900

Adjacent sequences:  A005007 A005008 A005009 * A005011 A005012 A005013

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Jun 14 1998

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 21 05:28 EST 2017. Contains 294988 sequences.