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A122055 A Somos 9-type recurrence: a(n) = (3*a(n-1)*a(n-8) - a(n-4)*a(n-5))/a(n-9), with a(0)=...=a(8)=1. 1
1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 5, 14, 41, 121, 353, 989, 2393, 9397, 49121, 342793, 2842633, 24619238, 211654405, 1731275594, 11581792513, 107195509553, 1126517154817, 16124559341513, 342648008481505, 8465982933121657, 213444061953471233 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,10

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..200

FORMULA

a(n) = (3*a(n-1)*a(n-8) - a(n-4)*a(n-5))/a(n-9).

MAPLE

a:= proc (n) option remember;

   if n < 9 then 1

   else (3*a(n-1)*a(n-8) - a(n-4)*a(n-5))/a(n-9)

   fi;

end proc;

seq(a(n), n=0..35); # G. C. Greubel, Oct 03 2019

MATHEMATICA

a[n_]:= a[n]= If[n<9, 1, (3*a[n-1]*a[n-8] -a[n-4]*a[n-5])/a[n-9]];

Table[a[n], {n, 0, 30}] (* modified by G. C. Greubel, Oct 03 2019 *)

PROG

(PARI) m=35; v=concat([1, 1, 1, 1, 1, 1, 1, 1, 1], vector(m-9)); for(n=10, m, v[n] = (3*v[n-1]*v[n-8] - v[n-4]*v[n-5])/v[n-9] ); v \\ G. C. Greubel, Oct 03 2019

(Magma) [n le 10 select 1 else (3*Self(n-1)*Self(n-8) - Self(n-4)*Self(n-5))/Self(n-9): n in [1..35]]; // G. C. Greubel, Oct 03 2019

(Sage)

def a(n):

    if n<10: return 1

    else: return (3*a(n-1)*a(n-8) - a(n-4)*a(n-5))/a(n-9)

[a(n) for n in (0..35)] # G. C. Greubel, Oct 03 2019

(GAP)

a:= function(n)

    if n<10 then return 1;

    else return (3*a(n-1)*a(n-8) - a(n-4)*a(n-5))/a(n-9);

    fi;

  end;

List([0..35], n-> a(n) ); # G. C. Greubel, Oct 03 2019

CROSSREFS

Cf. A122025.

Sequence in context: A116850 A116847 A116848 * A244885 A116845 A307466

Adjacent sequences:  A122052 A122053 A122054 * A122056 A122057 A122058

KEYWORD

nonn

AUTHOR

Roger L. Bagula, Sep 13 2006

EXTENSIONS

Name edited and offset changed by G. C. Greubel, Oct 03 2019

STATUS

approved

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Last modified September 30 08:54 EDT 2022. Contains 357104 sequences. (Running on oeis4.)