A247970 a(n) is the smallest k such that prime(k+i) (mod 6) takes successively the values 5,1,5,1... for i = 0, 1,...,n-1 ending with 1 or 5.

3, 3, 3, 3, 3, 3, 3, 24, 24, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140

Offset: 1

Author

Michel Lagneau, Sep 28 2014

Keywords

• nonn
• more

Comments

If a(22) exists, k > 10^5.

Examples

			a(1)= 3 => prime(3) (mod 6)= 5;
a(2)= 3 => prime(3) (mod 6)= 5, prime(4) (mod 6) = 1;
a(3)= 3 => prime(3) (mod 6)= 5, prime(4) (mod 6)= 1, prime(5) (mod 6)= 5.
		

Crossrefs

Cf. A039704, A247816, A247967, A247969.

Programs

Maple

with(numtheory):
for n from 1 to 35 do :
ii:=0:
   for k from 3 to 10^5 while (ii=0)do :
     s:=0:
      for i from 0 to n-1 do:
        r:=irem(ithprime(k+i),6):
        if r = irem(5^(i+1),6)
        then
        s:=s+1:
        else
        fi:
      od:
       if s=n and ii=0
       then
       printf ( "%d %d \n",n,k):ii:=1:
       else
       fi:
    od:
od: