A080214 Binomial(greatest prime factor of n, smallest prime factor of n).
1, 1, 1, 1, 1, 3, 1, 1, 1, 10, 1, 3, 1, 21, 10, 1, 1, 3, 1, 10, 35, 55, 1, 3, 1, 78, 1, 21, 1, 10, 1, 1, 165, 136, 21, 3, 1, 171, 286, 10, 1, 21, 1, 55, 10, 253, 1, 3, 1, 10, 680, 78, 1, 3, 462, 21, 969, 406, 1, 10, 1, 465, 35, 1, 1287, 55, 1, 136, 1771, 21, 1, 3, 1, 666, 10
Offset: 1
Links
- Antti Karttunen, Table of n, a(n) for n = 1..65537
Programs
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Mathematica
a[n_] := With[{f = FactorInteger[n]}, Binomial[f[[-1, 1]], f[[1, 1]]]]; Array[a, 100] (* Jean-François Alcover, Dec 02 2021 *) -
PARI
A080214(n) = if(1==n,n,my(f = factor(n), lpf = f[1, 1], gpf = f[#f~, 1]); binomial(gpf,lpf)); \\ Antti Karttunen, Sep 06 2018