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A151502
a(n) = A006720(n)^4 (fourth powers of Somos-4 sequence).
3
1, 1, 1, 1, 16, 81, 2401, 279841, 12117361, 9721171216, 5465500541281, 4541099550557761, 48178257964790528961, 148046697174216601867681, 3835980708567891638880403216, 258045180612631702971803868544561, 8100590302880631846481071607248577441
OFFSET
0,5
LINKS
FORMULA
a(n) = A028945(n)^2 = A006720(n)^4. - Seiichi Manyama, Nov 20 2016
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 *)
PROG
(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
(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
CROSSREFS
Cf. A006720(n)^k; A006720 (k=1), A028945 (k=2), A028935 (k=3), this sequence (k=4).
Sequence in context: A030514 A056571 A053909 * A030693 A308249 A285989
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 14 2009
STATUS
approved