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A193216
Least semiprime whose sum of prime factors equals n!
0
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.
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
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jul 18 2011
STATUS
approved