OFFSET
1,1
COMMENTS
The fastest way to calculate the complete list of class N primes up to P is to use the given formula (or PARI function nextclass()) with the list of class (N-1) primes up to P/2.
LINKS
FORMULA
{ a(n) } = { p = 2*m*A129248(k)+1 | k=1,2,3... and m=1,2,3... such that p is prime and m has no factor of class > 14- }
PROG
(PARI) class(n, s=1) = { if(!isprime(n), 0, if(!(n=factor(n+s)[, 1]) || n[ #n]<=3, 1, for(i=2, #n, n[1]=max(class(n[i], s)+1, n[1])); n[1]))}
nextclass(a, s=-1, p, n=[])={if(!p, p=nextprime(a[ #a]+1)); print("producing primes of class ", 1+class(a[1], s), ["+", "-"][1+(s<0)], " up to 2*", p); for(i=1, #a, for(k=1, p/a[i], if(isprime(2*k*a[i]-s), n=concat(n, 2*k*a[i]-s)))); vecsort(n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Apr 16 2007, Apr 21 2007
STATUS
approved