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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). 7
1, 4, 1, 19, 16, 56, 80, 383, 235 (list; graph; refs; listen; history; text; internal format)
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 A249716 A128041

Adjacent sequences:  A141230 A141231 A141232 * A141234 A141235 A141236

KEYWORD

nonn,changed

AUTHOR

Pierre CAMI, Jun 16 2008

STATUS

approved

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Last modified September 16 12:41 EDT 2019. Contains 327113 sequences. (Running on oeis4.)