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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A016129 Expansion of 1/((1-2x)(1-6x)). 20
1, 8, 52, 320, 1936, 11648, 69952, 419840, 2519296, 15116288, 90698752, 544194560, 3265171456, 19591036928, 117546237952, 705277460480, 4231664828416, 25389989101568, 152339934871552, 914039609753600 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n) = sum of n-th row in triangle A100851. - Reinhard Zumkeller, Nov 20 2004

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..900

Index entries for linear recurrences with constant coefficients, signature (8,-12)

FORMULA

a(n)= A071951(n+2, 2) = 9*(2*3)^(n-1) - (2*1)^(n-1) = (2^(n-1))*(3^(n+1)-1), n>=0. - Wolfdieter Lang, Nov 07 2003

From Lambert Klasen (lambert.klasen(AT)gmx.net), Feb 05 2005: (Start)

G.f.: 1/((1-2*x)*(1-6*x)).

E.g.f.: (-exp(2*x) + 3*exp(6*x))/2.

a(n) = (6^(n+1) - 2^(n+1))/4. (End)

a(n)^2 = A144843(n+1). - Philippe Deléham, Nov 26 2008

a(n-1) = ((4+sqrt4)^n - (4-sqrt4)^n)/4 in Fibonacci form. - Al Hakanson (hawkuu(AT)gmail.com), Dec 31 2008

a(n) = 8*a(n-1) - 12*a(n-2). - Philippe Deléham, Jan 01 2009

a(n) = det(|ps(i+2,j+1)|, 1 <= i,j <= n), where ps(n,k) are Legendre-Stirling numbers of the first kind (A129467). - Mircea Merca, Apr 06 2013

MATHEMATICA

Join[{a=1, b=8}, Table[c=8*b-12*a; a=b; b=c, {n, 60}]] (* Vladimir Joseph Stephan Orlovsky, Jan 19 2011 *)

CoefficientList[Series[1/((1-2x)(1-6x)), {x, 0, 30}], x] (* or *) LinearRecurrence[{8, -12}, {1, 8}, 30] (* Harvey P. Dale, Jan 15 2015 *)

PROG

(Sage) [lucas_number1(n, 8, 12) for n in xrange(1, 21)] # Zerinvary Lajos, Apr 23 2009

(Sage) [(6^n - 2^n)/4 for n in xrange(1, 21)] # Zerinvary Lajos, Jun 04 2009

(MAGMA) [(6^(n+1)-2^(n+1))/4 : n in [0..20]]; // Vincenzo Librandi, Oct 09 2011

(PARI) Vec(1/(1-2*x)/(1-6*x)+O(x^99)) \\ Charles R Greathouse IV, Apr 17 2012

CROSSREFS

Cf. A089278, A089500.

Sequence in context: A257285 A125345 A111996 * A006631 A205218 A287813

Adjacent sequences:  A016126 A016127 A016128 * A016130 A016131 A016132

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 19 06:59 EDT 2019. Contains 322237 sequences. (Running on oeis4.)