A141725 a(n) = 4^(n+1) - 3.
1, 13, 61, 253, 1021, 4093, 16381, 65533, 262141, 1048573, 4194301, 16777213, 67108861, 268435453, 1073741821, 4294967293, 17179869181, 68719476733, 274877906941, 1099511627773, 4398046511101, 17592186044413, 70368744177661
Offset: 0
Links
- Vincenzo Librandi, Table of n, a(n) for n = 0..1000
- John Elias, Illustration of Initial Terms: Sierpinski Square Curve
- Mattia Fregola, Elementary Cellular Automata Rule 1 generating OEIS sequence A277799, A058896, A141725, A002450
- Index entries for linear recurrences with constant coefficients, signature (5,-4).
Programs
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GAP
List([0..25], n -> 4^(n+1)-3); # Muniru A Asiru, Feb 20 2018
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Magma
[4^(n+1)-3: n in [0..30]]; // Vincenzo Librandi, Aug 08 2011
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Maple
a:= n-> 4^(n+1)-3: seq(a(n), n=0..25); # Muniru A Asiru, Feb 20 2018
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Mathematica
4^(Range[2,25]-1)-3 (* or *) LinearRecurrence[{5,-4},{1,13},25] (* or *) NestList[4#+9&,1,25] (* Harvey P. Dale, Sep 25 2011 *)
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PARI
a(n)=4^(n+1)-3 \\ Charles R Greathouse IV, Oct 07 2015
Formula
a(n) = 4*a(n-1) + 9 for n > 0, a(0) = 1.
a(n) = A036563(2*n+2).
G.f.: (1 + 8*x)/((1 - x)*(1 - 4*x)). - R. J. Mathar, Sep 13 2008
a(n) = 4^n - 3, with offset 1. - Omar E. Pol, Aug 22 2011
a(n) = 5*a(n-1) - 4*a(n-2) for n > 1, a(0) = 1, a(1) = 13. - Harvey P. Dale, Sep 25 2011
E.g.f.: exp(4*x) - 3*exp(x). - Elmo R. Oliveira, Nov 15 2023
Extensions
Edited by N. J. A. Sloane, Sep 13 2008
More terms from R. J. Mathar, Sep 13 2008
Comments