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

3,1

Comments

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

Links

Table of n, a(n) for n=3..20.

Example

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.

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:

Crossrefs

Cf. A073046.

Sequence in context: A057782 A115071 A000562 * A213019 A098450 A337269

Adjacent sequences: A193213 A193214 A193215 * A193217 A193218 A193219

Keyword

nonn

Author

Michel Lagneau, Jul 18 2011

Status

approved