|
|
A180325
|
|
a(n) = k is the smallest number such that n is the number of distinct primes dividing k! + 1.
|
|
0
|
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
A greedy inverse to A066856. - R. J. Mathar, Jan 21 2011
|
|
LINKS
|
|
|
EXAMPLE
|
a(6) = 18 because the 6 distinct primes dividing 18! + 1 = 6402373705728001
are {19, 23, 29, 61, 67, 123610951}.
|
|
MAPLE
|
with(numtheory):for n from 1 to 7 do:ind:=0:for k from 1 to 50 while(ind=0)
do: x:=k!+1:y:=nops(factorset(x)):if y=n then ind:=1:printf(`%d, `, k):else fi:od:
od:
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,hard
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|