OFFSET
1,1
COMMENTS
k*p(n)#-p(n+1) is the greatest prime < k*p(n)#-p(n+1)-1 and if k*p(n)#-p(n+1)-1 is not prime it is the greatest prime < k*p(n)#-p(n+1) P is given in one other sequence
EXAMPLE
1*2*3*5*7*11*13-17=30013, 1*p(6)#-p(7)=30013, 1 is the least k for n=6
30013 is prime
a(7)=2 since 2*17#-19 = 1021001 is prime.
PROG
(PARI) primorial(n) = prod(i=1, primepi(n), prime(i)) A090189(n) = {local(k, a, b); k=1; a=primorial(prime(n)); b=prime(n+1); while(!isprime(a*k-b), k++); k}
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Pierre CAMI, Jan 21 2004
EXTENSIONS
a(7) corrected by Michael B. Porter, Jan 29 2010
STATUS
approved