

A098594


Numbers n such that n!1 and n!+1 are both semiprime.


0




OFFSET

1,1


COMMENTS

This sequence is formed of all those terms that appear in both A078778 and A078781.
No more terms < 307.  David Wasserman, Feb 26 2008
a(11) >= 464.  D. S. McNeil, Sep 04 2011
a(11) >= 929. 929!1 is semiprime, no factor of 929!+1 is known.  Sean A. Irvine, Mar 09 2013


LINKS

Table of n, a(n) for n=1..10.


EXAMPLE

10!+1 = 3628801 = 11*329891 and 10!1 = 3628799 = 29*125131 so 10 is a member of the sequence.
464 is not a term since 464!1=2828197538205421590987128183441789966021011*C996 is not a semiprime.  Sean A. Irvine, Mar 09 2013


MAPLE

out:=[]: for n from 1 to 60 do: a:=n!1: b:=n!+1: if (bigomega(a)=2) and (bigomega(b)=2) then out:=[op(out), n]: print(n): fi: od: out;


CROSSREFS

Cf. A078778, A078781.
Sequence in context: A032717 A256360 A205676 * A154315 A182084 A262707
Adjacent sequences: A098591 A098592 A098593 * A098595 A098596 A098597


KEYWORD

hard,more,nonn


AUTHOR

Mark Hudson (mrmarkhudson(AT)hotmail.com), Sep 17 2004


EXTENSIONS

a(10) from D. S. McNeil, Sep 04 2011


STATUS

approved



