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A064268
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a(n) = (a(n-1) * a(n-6) + 2 * a(n-3) * a(n-4)) / a(n-7). a(1) = ... = a(7) = 1. Somos-7 variation.
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1
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1, 1, 1, 1, 1, 1, 1, 3, 5, 7, 13, 43, 113, 521, 1241, 3681, 23657, 177721, 679505, 4674203, 27273277, 275517767, 3496390229, 37043734803, 226196947873, 4391322667601, 81041508965617, 1433151398896001, 25397505914206225
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,8
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,100
Index entries for two-way infinite sequences
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FORMULA
| a(8 - n) = a(n).
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PROG
| (PARI) {a(n) = if( n<1, a(8-n), if( n<8, 1, (a(n-1) * a(n-6) + 2 * a(n-3) * a(n-4)) / a(n-7)))}
(PARI) { a7=a6=a5=a4=a3=a2=a1=a=1; for (n=1, 100, if (n>7, a=(a1*a6 + 2*a3*a4)/a7; a7=a6; a6=a5; a5=a4; a4=a3; a3=a2; a2=a1; a1=a); write("b064268.txt", n, " ", a) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 10 2009]
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CROSSREFS
| Cf. A006723.
Sequence in context: A057187 A163080 A141414 * A118743 A114980 A024372
Adjacent sequences: A064265 A064266 A064267 * A064269 A064270 A064271
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KEYWORD
| nonn,easy
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AUTHOR
| Michael Somos, Sep 24, 2001
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