OFFSET
1,1
COMMENTS
There are a maximum of 2^n numbers which arise as the products of the subsets of the first n natural numbers. The actual number is smaller because of repetitions. Then a(n) = the greatest prime obtained on adding 1 to each of these numbers.
Different from A089136 (see the comments there).
LINKS
Martin Fuller, Table of n, a(n) for n = 1..200
EXAMPLE
a(5) = 61 = 3*4*5 + 1. 5! + 1, 4!+ 1, are composite and 2*4*5 + 1 = 41 <61, etc.
MATHEMATICA
Do[l = Map[Times @@ #&, Subsets[Range[n]]]; Print[Max[Select[Map[ #+1&, l], PrimeQ]]], {n, 20}] (* Ryan Propper, Aug 13 2005 *)
f[n_] := Max@ Select[ Union[ Times @@@ Subsets@ Range@ n] + 1, PrimeQ]; Array[f, 20] (* Robert G. Wilson v, Nov 13 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Mar 26 2004
EXTENSIONS
More terms from Ryan Propper, Aug 13 2005
STATUS
approved