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A080215
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Binomial(greatest prime factor of n, smallest odd prime factor of n).
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2
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1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 10, 2, 1, 1, 1, 1, 35, 1, 1, 1, 1, 1, 1, 1, 1, 10, 1, 2, 165, 1, 21, 1, 1, 1, 286, 1, 1, 35, 1, 1, 10, 1, 1, 1, 1, 1, 680, 1, 1, 1, 462, 1, 969, 1, 1, 10, 1, 1, 35, 2, 1287, 165, 1, 1, 1771, 21, 1, 1, 1, 1, 10, 1, 330, 286, 1, 1, 1, 1, 1, 35
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OFFSET
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1,2
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LINKS
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FORMULA
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MATHEMATICA
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a[n_] := With[{f = Select[FactorInteger[n], #[[1]] != 2&]}, If[f == {}, 2, Binomial[f[[-1, 1]], f[[1, 1]]]]];
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PROG
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(PARI) A080215(n) = if(1==n, n, my(f = factor(n)[, 1], v = select(x->((x%2)==1), f)); binomial(f[#f], if(#v, vecmin(v), 1))); \\ Antti Karttunen, Dec 23 2018
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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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