|
| |
|
|
A020704
|
|
Pisot sequences E(3,10), P(3,10).
|
|
1
|
|
|
|
3, 10, 33, 109, 360, 1189, 3927, 12970, 42837, 141481, 467280, 1543321, 5097243, 16835050, 55602393, 183642229, 606529080, 2003229469, 6616217487, 21851881930, 72171863277, 238367471761, 787274278560, 2600190307441, 8587845200883, 28363725910090
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
0,1
|
|
|
LINKS
|
|
|
|
FORMULA
|
a(n) = 3*a(n-1) + a(n-2) (holds at least up to n = 1000 but is not known to hold in general).
a(n) = (2^(-1-n)*((3-sqrt(13))^n*(-11+3*sqrt(13)) + (3+sqrt(13))^n*(11+3*sqrt(13))))/sqrt(13).
G.f.: (3+x) / (1-3*x-x^2).
(End)
Theorem: For E(3,10), a(n) = 3 a(n - 1) + a(n - 2) for n>=2. Proved using the PtoRv program of Ekhad-Sloane-Zeilberger, and implies the above conjectures. - N. J. A. Sloane, Sep 09 2016
|
|
|
MATHEMATICA
|
RecurrenceTable[{a[0] == 3, a[1] == 10, a[n] == Floor[a[n - 1]^2/a[n - 2] + 1/2]}, a, {n, 0, 30}] (* Bruno Berselli, Feb 05 2016 *)
|
|
|
PROG
|
(Magma) Exy:=[3, 10]; [n le 2 select Exy[n] else Floor(Self(n-1)^2/Self(n-2) + 1/2): n in [1..30]]; // Bruno Berselli, Feb 05 2016
|
|
|
CROSSREFS
|
See A008776 for definitions of Pisot sequences.
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
|
|
|
STATUS
|
approved
|
| |
|
|
