A129475 Primes of Erdos-Selfridge class 15+.

23869461181, 39279010921, 45608421601, 58345550881, 64788537493, 79681330633, 83807064853, 86315197987, 91658731403, 97331927117, 102581556673, 104758832257, 106426256653, 111136152961, 111795382441, 125586978001, 143216767091, 144155203267, 144708098881

Offset: 1

Author

M. F. Hasler, Apr 16 2007

Keywords

• nonn

Comments

a(1..19) calculated using A129474 up to 75e9, which gives A129475(20) > 150e9. This is enough to ensure that 288310406533 = A005113(16).

Examples

			23869461181 = 1+2*7*1704961513, where 1704961513 is in A129474
		

Links

• 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)}
A129475=nextclass(A129474)

Formula

{ a(n) } = { p = 2*m*A129474(k)-1 | k=1,2,3... and m=1,2,3... such that p is prime and m has no factor of class > 14+ }

Extensions

Extended to a(19) by M. F. Hasler, Jan 12 2014