login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A193216 Least semiprime whose sum of prime factors equals n! 0

%I

%S 9,95,791,7799,85391,1248959,4717271,39916679,518918231,6227020631,

%T 143221477871,1482030950111,61460695293791,1108907864061191,

%U 20985558257660519,262497321934846319,12286155141292021799,75419962253475839039

%N Least semiprime whose sum of prime factors equals n!

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

%e 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.

%p 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:

%Y Cf. A073046.

%K nonn

%O 3,1

%A _Michel Lagneau_, Jul 18 2011

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 19 19:28 EDT 2021. Contains 347564 sequences. (Running on oeis4.)