A129249 Primes of Erdos-Selfridge class 15-.

1432349099, 1749565397, 2771868719, 3790874279, 5288908679, 5804138567, 6273146879, 8123301983, 8594094589, 11055501923, 11809566403, 11914176299, 12647401799, 13432673083, 13925010299, 14208729979

Offset: 1

Author

M. F. Hasler, Apr 16 2007, Apr 21 2007

Keywords

• nonn

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

• M. F. Hasler, Table of n, a(n) for n = 1..48
• Index entries for sequences related to the Erdos-Selfridge classification

Programs

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)}
A129249=nextclass(A129248)

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- }