A239656 First differences of sphenic numbers, cf. A007304.

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, 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, 12, 12, 4, 21, 6, 13, 8, 8, 5, 3, 4, 4, 3, 1, 5, 3, 9, 11, 4

Offset: 1

Author

Reinhard Zumkeller, Mar 23 2014

Keywords

• nonn

Comments

a(n) = A007304(n+1) - A007304(n);

see A239673 and A239674 for record values and where they occur: A239673(n) = a(A239674(n)).

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A065516.

Programs

Haskell

a239656 n = a239656_list !! (n-1)
a239656_list = zipWith (-) (tail a007304_list) a007304_list

Maple

A007304 := proc(n)
    option remember;
    if n = 1 then
        30;
    else
        for a from procname(n-1)+1 do
            if numtheory[bigomega](a) =3 and nops(numtheory[factorset](a)) = 3 then
                return a;
            end if;
        end do:
    end if;
end proc:
A239656 := proc(n)
    A007304(n+1)-A007304(n) ;
end proc:

Mathematica

With[{upto=1000},Differences[Sort[Select[Times@@@Subsets[Prime[ Range[ Ceiling[upto/6]]],{3}],#<=upto&]]]] (* Harvey P. Dale, Jan 08 2015 *)