|
%I #8 Jan 08 2015 19:31:03
%S 12,24,4,8,24,3,5,4,16,8,16,11,5,4,8,4,4,5,27,8,1,7,8,9,3,8,7,9,3,1,4,
%T 20,8,4,23,9,3,9,4,4,11,14,3,4,4,8,8,3,1,4,1,3,4,13,10,5,4,9,11,4,8,
%U 12,12,4,21,6,13,8,8,5,3,4,4,3,1,5,3,9,11,4
%N First differences of sphenic numbers, cf. A007304.
%C a(n) = A007304(n+1) - A007304(n);
%C see A239673 and A239674 for record values and where they occur: A239673(n) = a(A239674(n)).
%H Reinhard Zumkeller, <a href="/A239656/b239656.txt">Table of n, a(n) for n = 1..10000</a>
%p A007304 := proc(n)
%p option remember;
%p if n = 1 then
%p 30;
%p else
%p for a from procname(n-1)+1 do
%p if numtheory[bigomega](a) =3 and nops(numtheory[factorset](a)) = 3 then
%p return a;
%p end if;
%p end do:
%p end if;
%p end proc:
%p A239656 := proc(n)
%p A007304(n+1)-A007304(n) ;
%p end proc:
%t With[{upto=1000},Differences[Sort[Select[Times@@@Subsets[Prime[ Range[ Ceiling[upto/6]]],{3}],#<=upto&]]]] (* _Harvey P. Dale_, Jan 08 2015 *)
%o (Haskell)
%o a239656 n = a239656_list !! (n-1)
%o a239656_list = zipWith (-) (tail a007304_list) a007304_list
%Y Cf. A065516.
%K nonn
%O 1,1
%A _Reinhard Zumkeller_, Mar 23 2014
|
