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A038508
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Expansion of (1-2*x-x^2)/((1-2*x)*(1-2*x+2*x^2)).
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2
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1, 2, 5, 12, 30, 76, 196, 512, 1352, 3600, 9648, 25984, 70240, 190400, 517184, 1406976, 3831936, 10445056, 28488448, 77735936, 212186624, 579320832, 1581966336, 4320477184, 11800692736, 32233951232
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OFFSET
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0,2
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COMMENTS
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Number of (s(0), s(1), ..., s(n+1)) such that 0 < s(i) < 6 and |s(i) - s(i-1)| <= 1 for i = 1,2,...,n+1, s(0) = 1, s(n+1) = 2. - Herbert Kociemba, Jun 17 2004
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LINKS
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FORMULA
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a(n) = (3*2^(n+1) - sqrt(3)*(1-sqrt(3))^(n+1) + sqrt(3)*(1+sqrt(3))^(n+1))/12. - Herbert Kociemba, Jun 17 2004
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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