A271955 Somos's sequence {b(8,n)} defined in comment in A078495: a(0)=a(1)=...=a(18)=1; for n>=19, a(n)=(a(n-1)*a(n-18)+a(n-9)*a(n-10))/a(n-19).

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 18, 30, 50, 80, 122, 178, 250, 340, 800, 1308, 1924, 2780, 4136, 6452, 10476, 17348, 28720, 61664, 179696, 439304, 910464, 1686704, 2905792, 4793624, 7753616, 12537856

Offset

0,20

Links

Seiichi Manyama, Table of n, a(n) for n = 0..533

Mathematica

a[k_, n_]:=a[k, n]=If[n>2k+2, (a[k, (n-1)]*a[k, (n-2k-2)]+a[k, (n-k-1)]*a[k, (n-k-2)])/a[k, (n-2k-3)], 1];
Map[a[8, #]&, Range[0, 50]] (* Peter J. C. Moses, Apr 17 2016 *)

Prog

(PARI) {a(n) = if(n<= 19, 1, (a(n-1)*a(n-18) + a(n-9)*a(n-10))/a(n-19))}; for(n=1, 50, print1(a(n), ", ")) \\ G. C. Greubel, Jul 30 2018
(Magma) [n le 19 select 1 else (Self(n-1)*Self(n-18)+Self(n-9)*Self(n-10))/Self(n-19): n in [1..60]]; // G. C. Greubel, Jul 30 2018

Crossrefs

Cf. A006721, A078495, A268199, A271948, A271949, A271950, A271952, A271954.

Sequence in context: A110806 A357769 A180468 * A365420 A342650 A328273

Adjacent sequences: A271952 A271953 A271954 * A271956 A271957 A271958

Keyword

nonn

Author

Vladimir Shevelev and Peter J. C. Moses, Apr 17 2016

Status

approved