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A066048 Product of smallest and greatest prime factors of n.

%I A066048 #20 Jun 17 2018 01:57:07
%S A066048 1,4,9,4,25,6,49,4,9,10,121,6,169,14,15,4,289,6,361,10,21,22,529,6,25,
%T A066048 26,9,14,841,10,961,4,33,34,35,6,1369,38,39,10,1681,14,1849,22,15,46,
%U A066048 2209,6,49,10,51,26,2809,6,55,14,57,58,3481,10,3721,62,21,4,65,22,4489,34
%N A066048 Product of smallest and greatest prime factors of n.
%C A066048 For all n > 1, a(n) is semiprime; n is semiprime iff a(n) = n; n is prime iff a(n) = n^2;
%C A066048 For all primes p and k > 0, a(p^k) = p^2.
%H A066048 R. Zumkeller, <a href="/A066048/b066048.txt">Table of n, a(n) for n = 1..10000</a>
%F A066048 a(n) = A020639(n) * A006530(n).
%t A066048 f[n_] := Transpose[ FactorInteger[n]][[1]]; Table[ First[f[n]]*Last[f[n]], {n, 2, 100} ]
%t A066048 p[n_]:=Module[{fctrs=Transpose[FactorInteger[n]][[1]]},First[fctrs] Last[fctrs]]; Array[p,70] (* _Harvey P. Dale_, Jun 11 2011 *)
%o A066048 (PARI) { for (n = 1, 10000, if (n==1, a=1, f=factor(n)~; a=f[1, 1] * f[1, length(f)]); write("b066048.txt", n, " ", a) ) } \\ _Harry J. Smith_, Nov 08 2009
%Y A066048 Cf. A000040, A001358, A001248, A000961.
%Y A066048 Cf. A130064, A130065.
%K A066048 nonn,nice,easy
%O A066048 1,2
%A A066048 _Reinhard Zumkeller_
%E A066048 More terms from _Robert G. Wilson v_, Jan 03 2002