A229626 a(n) is the smallest m such that 2*m^k-1 is prime for k = 1, 2, ..., n.

2, 2, 3, 6, 6, 11256895, 15682744, 45779314036, 687860415949

Offset

1,1

Links

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

Mathematica

a[1]=2; a[n_]:=a[n]=(For[m=a[n-1], Union[Table[PrimeQ[2 m^k-1], {k, n}]]!={True}, m++]; m)

Prog

(PARI) a(n)=my(m=2); while(1, for(k=1, n, if(!ispseudoprime(2*m^k-1), m++; next(2))); return(m)) \\ Charles R Greathouse IV, Oct 01 2013

Crossrefs

Cf. A229627.

Sequence in context: A078921 A011961 A182713 * A358088 A091770 A032058

Adjacent sequences: A229623 A229624 A229625 * A229627 A229628 A229629

Keyword

nonn,more

Author

Farideh Firoozbakht, Sep 27 2013

Extensions

a(8) from Giovanni Resta, Oct 01 2013

a(9) from Tyler Busby, Jan 06 2023

Status

approved