A151502 a(n) = A006720(n)^4 (fourth powers of Somos-4 sequence).

1, 1, 1, 1, 16, 81, 2401, 279841, 12117361, 9721171216, 5465500541281, 4541099550557761, 48178257964790528961, 148046697174216601867681, 3835980708567891638880403216, 258045180612631702971803868544561, 8100590302880631846481071607248577441

Offset: 0

Author

N. J. A. Sloane, May 14 2009

Keywords

• nonn

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..76

Crossrefs

Cf. A006720(n)^k; A006720 (k=1), A028945 (k=2), A028935 (k=3), this sequence (k=4).

Programs

Magma

I:=[1,1,1,1]; [n le 4 select I[n] else ((Self(n-1)*Self(n-3) + Self(n-2)^2)/Self(n-4))^4: n in [1..15]]; // G. C. Greubel, Sep 25 2018

Mathematica

b[n_ /; 0 <= n <= 4] = 1; b[n_]:= b[n] = (b[n-1]*b[n-3] + b[n-2]^2)/b[n -4]; Table[(b[n])^4, {n, 0, 20}] (* G. C. Greubel, Sep 25 2018 *)

PARI

{b(n) = if(n<4, 1, (b(n-1)*b(n-3) + b(n-2)^2)/b(n-4))};
for(n=0, 20, print1((b(n))^4, ", ")) \\ G. C. Greubel, Sep 25 2018

PARI

b=vector(20); b[1]=b[2]=b[3]=1;b[4]=2; for(n=5, #b, b[n]=(b[n-1]*b[n-3]+b[n-2]^2)/b[n-4]); concat(1, vector(20, n, b[n]^4)) \\ Altug Alkan, Sep 25 2018

Formula

a(n) = A028945(n)^2 = A006720(n)^4. - Seiichi Manyama, Nov 20 2016