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A340259
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a(n) = A340312(n, 2^(n-1)). a(n) is the central term of row n of A340312.
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2
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OFFSET
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1,3
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COMMENTS
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a(9) = 2299131884087642202247291403507120751687796592498104258 * C, where C is a composite factor with 96 digits.
C = P47*P49, with P47 = 88967307877356450624418823383132738084943851019 and
P49 = 4512180962860489443011495305279720577473472225641. - Hugo Pfoertner, Jan 09 2021
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LINKS
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FORMULA
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a(n) = (2*binomial(2^n-1, 2^(n-1)) + (2^n-1)*binomial(2^(n-1), 2^(n-2)))/2^n for n >= 3. - Andrew Howroyd, Jan 09 2021
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MAPLE
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seq(A340312_row(n)[2^(n-1)+1], n = 1..8);
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PROG
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(PARI) a(n) = {if(n<=2, n==1, (2*binomial(2^n-1, 2^(n-1)) + (2^n-1)*binomial(2^(n-1), 2^(n-2)))/2^n)} \\ Andrew Howroyd, Jan 09 2021
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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