A141233 Sequence of k such that starting with P(0)=7 then k(n)*P(n-1)*(k(n)*P(n-1)-1)-1 is the least prime = P(n).

1, 4, 1, 19, 16, 56, 80, 383, 235

Offset

1,2

Links

Table of n, a(n) for n=1..9.

Example

1*7*7-1*7-1=41 prime so k(1)=1 P(1)=41;
1*41*(1*41-1)-1=1639 composite,
2*41*(2*41-1)-1=6641 composite,
3*41*(3*41-1)-1=15005 composite,
4*41*(4*41-1)-1=26731 prime so k(2)=4 P(2)=26731;
1*26731*(1*26731-1)-1=714519629 prime so k(3)=1 P(3)=714519629.

Prog

(PARI) P=7; for(i=1, 20, k=0; while(!ispseudoprime(t=k++*P*(k*P-1)-1), ); P=t; print1(k", ")) \\ Michel Marcus, Sep 16 2019 ; after A141240

Crossrefs

Cf. A141234, A141235, A141236, A141237, A141238, A141239, A141240.

Sequence in context: A192722 A300141 A057968 * A055139 A349708 A249716

Adjacent sequences: A141230 A141231 A141232 * A141234 A141235 A141236

Keyword

nonn,more

Author

Pierre CAMI, Jun 16 2008

Status

approved