A193216 Least semiprime whose sum of prime factors equals n!

9, 95, 791, 7799, 85391, 1248959, 4717271, 39916679, 518918231, 6227020631, 143221477871, 1482030950111, 61460695293791, 1108907864061191, 20985558257660519, 262497321934846319, 12286155141292021799, 75419962253475839039

Offset: 3

Author

Michel Lagneau, Jul 18 2011

Keywords

• nonn

Comments

Write n! = p+q (p,q prime), p*q minimal; then a(n)=p*q. Subset of A073046.

Examples

			a(4) = 95 because,for n=4, 4! = 24; 24 = 5 + 19 = 7 + 17 = 11 + 13; 5*19 is minimal => p*q = 5*19 = 95.
		

Crossrefs

Cf. A073046.

Programs

Maple

 with(numtheory):for n from 3 to 20 do:x:=n!:id:=0:for m from 2 to 10000 while(id=0) do:p:=ithprime(m):y:=x-p:if type(y,prime)=true then z:=y*p: id:=1:printf(`%d, `, z): else fi:od:od: