OFFSET
0,1
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = 3*a(n-1) - 2*a(n-2) + a(n-3) + a(n-4) - 2*a(n-5) + a(n-6) - a(n-7) (conjectured). Recurrence is satisfied for at least 760000 terms. - Chai Wah Wu, Jul 25 2016
Note the warning in A010925 from Pab Ter (pabrlos(AT)yahoo.com), May 23 2004: [A010925] and other examples show that it is essential to reject conjectured generating functions for Pisot sequences until a proof or reference is provided. - N. J. A. Sloane, Jul 26 2016
MATHEMATICA
a[n_] := a[n] = Switch[n, 0, 4, 1, 9, _, Ceiling[a[n-1]^2/a[n-2]]];
a /@ Range[0, 29] (* Jean-François Alcover, Oct 22 2019 *)
PROG
(PARI) pisotL(nmax, a1, a2) = {
a=vector(nmax); a[1]=a1; a[2]=a2;
for(n=3, nmax, a[n] = ceil(a[n-1]^2/a[n-2]));
a
}
pisotL(50, 4, 9) \\ Colin Barker, Aug 07 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved