p + primorial/p is prime
Leroy Quet
q1qq2qqq3qqqq at yahoo.com
Sun Jun 1 18:57:04 CEST 2008
Could someone please calculate some terms of this
sequence?
I wonder if it is already in the EIS.
a(n) = the number of primes p, p <= the nth
prime, where
p + (1/p)product{k=1 to n} p(k)
is prime, where p(k) is the kth prime.
The sequence begins (unless I errrd...):
1,2,3,4,3,...
For example,
For n = 5:
2 + 3*5*7*11 = 13*89;
3 + 2*5*7*11 = 773 = prime;
5 + 2*3*7*11 = 467 = prime;
7 + 2*3*5*11 = 337 = prime;
11 + 2*3*5*7 = 221 = 13*17.
So, a(5) = 3.
Maybe the sequence is already in the EIS which
counts the number of such sums that are
COMPOSITE.
Thanks,
Leroy Quet
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