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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

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OFFSET

1,1

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

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 *)

PROG

(Haskell)

a239656 n = a239656_list !! (n-1)

a239656_list = zipWith (-) (tail a007304_list) a007304_list

CROSSREFS

Cf. A065516.

Sequence in context: A333933 A015447 A072822 * A059161 A133491 A075606

Adjacent sequences: A239653 A239654 A239655 * A239657 A239658 A239659

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Mar 23 2014

STATUS

approved