A271831 Somos's sequence {a(6,n)} defined in comment in A018896: a(0)=a(1)= ... = a(13) = 1; for n>=14, a(n) = (a(n-1)*a(n-13) + a(n-7)^2)/a(n-14).

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 12, 21, 37, 62, 98, 147, 358, 609, 959, 1541, 2618, 4655, 8407, 28631, 81011, 186528, 376741, 706041, 1280174, 3598503, 8411236, 24021605, 74880071, 219318499, 580374907, 1400227135, 6308924342

Offset: 0

Author

Vladimir Shevelev and Peter J. C. Moses, Apr 15 2016

Keywords

• nonn

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..416
• Eric Weisstein's World of Mathematics, Somos Sequence

Crossrefs

Cf. A018896, A006125, A006720, A102276, A271341, A271835, A271837, A271838, A271839.

Programs

Magma

[n le 14 select 1 else (Self(n-1)*Self(n-13) + Self(n-7)^2)/Self(n-14): n in [1..50]]; // G. C. Greubel, Feb 21 2018

Mathematica

a[n_ /; 0 <= n <= 14] = 1; a[n_]:= a[n] = (a[n-1]*a[n-13] + a[n-7]^2)/a[n -14]; Table[a[n], {n,0,50}] (* G. C. Greubel, Feb 21 2018 *)

PARI

{a(n) = if(n<= 14, 1, (a(n-1)*a(n-13) + a(n-7)^2)/a(n-14))};
for(n=1,50, print1(a(n), ", ")) \\ G. C. Greubel, Feb 21 2018