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A058058
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Generalized Somos-7 sequence: a(n)*a(n+7) = 3*a(n+1)*a(n+6) - 4*a(n+2)* a(n+5) + 4*a(n+3)*a(n+4).
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1
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1, 1, 1, 1, 1, 1, 1, 3, 9, 19, 33, 131, 681, 3921, 23801, 132881, 598121, 7466321, 141401273, 1865484899, 19358862929, 314151573363, 7831607063961, 237725833277411, 8937694547422641, 293153245305595201, 7098035759907924561, 310194702846756799041, 35075042744420641281841
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OFFSET
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1,8
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REFERENCES
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N. Elkies, posting to the NMBRTHRY(AT)LISTSERV.NODAK.EDU newsgroup, Nov. 2000.
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LINKS
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G. C. Greubel, Table of n, a(n) for n = 1..170
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MATHEMATICA
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a[1] =a[2] =a[3] =a[4] =a[5] =a[6] =a[7] =1; a[n_]:= a[n] = (3*a[n-1]*a[n-6] - 4*a[n-2]*a[n-5] + 4*a[n-3]*a[n-4])/a[n-7]; Table[ a[n], {n, 1, 35}]
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PROG
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(PARI) {a(n) = if (n <=7, 1, (3*a(n-1)*a(n-6) - 4*a(n-2)*a(n-5) + 4*a(n-3)*a(n-4))/a(n-7))};
for(n=1, 30, print1(a(n), ", ")) \\ G. C. Greubel, Feb 21 2018
(MAGMA) I:=[1, 1, 1, 1, 1, 1, 1]; [n le 7 select I[n] else (3*Self(n-1)*Self(n-6) - 4*Self(n-2)*Self(n-5) + 4*Self(n-3)*Self(n-4))/Self(n-7): n in [1..30]]; // G. C. Greubel, Feb 21 2018
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CROSSREFS
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Cf. A006720, A006721, A006722 and A006723.
Sequence in context: A147119 A146184 A155274 * A062748 A325666 A147174
Adjacent sequences: A058055 A058056 A058057 * A058059 A058060 A058061
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v, Nov 20 2000
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STATUS
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approved
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