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A229626
a(n) is the smallest m such that 2*m^k-1 is prime for k = 1, 2, ..., n.
3
2, 2, 3, 6, 6, 11256895, 15682744, 45779314036, 687860415949
OFFSET
1,1
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
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