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A140504 a(n) = 2^n + 4. 15
5, 6, 8, 12, 20, 36, 68, 132, 260, 516, 1028, 2052, 4100, 8196, 16388, 32772, 65540, 131076, 262148, 524292, 1048580, 2097156, 4194308, 8388612, 16777220, 33554436, 67108868, 134217732, 268435460, 536870916, 1073741828 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(n) = A173786(n,2) for n>1; a(n+2)*A028399(n) = A175164(2*n). [Reinhard Zumkeller, Feb 28 2010]

LINKS

Table of n, a(n) for n=0..30.

Index entries for linear recurrences with constant coefficients, signature (3,-2).

FORMULA

G.f.: (5-9*x)/((1-x)*(1-2*x)). [Jaume Oliver Lafont, Aug 30 2009]

a(n) = 2*a(n-1)-4 (with a(0)=5). [Vincenzo Librandi, Nov 24 2009]

MATHEMATICA

Table[2^n + 4, {n, 0, 30}] (* Stefan Steinerberger, Aug 04 2008 *)

LinearRecurrence[{3, -2}, {5, 6}, 40] (* Harvey P. Dale, May 26 2018 *)

PROG

(Sage) [gaussian_binomial(n, 1, 2)+5 for n in xrange(0, 31)] # Zerinvary Lajos, May 31 2009

(PARI) a(n)=2^n+4 \\ Charles R Greathouse IV, Dec 21 2011

CROSSREFS

Sequence in context: A193569 A032721 A105106 * A120131 A047437 A188054

Adjacent sequences:  A140501 A140502 A140503 * A140505 A140506 A140507

KEYWORD

nonn,easy

AUTHOR

Paul Curtz, Jun 30 2008

EXTENSIONS

More terms from Stefan Steinerberger, Aug 04 2008

STATUS

approved

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Last modified October 14 14:26 EDT 2019. Contains 328018 sequences. (Running on oeis4.)