

A268707


Smallest ndigit prime having at least n1 digits equal to 9.


6



2, 19, 199, 1999, 49999, 199999, 2999999, 19999999, 799999999, 9199999999, 59999999999, 959999999999, 9919999999999, 59999999999999, 499999999999999, 9299999999999999, 99919999999999999, 994999999999999999, 9991999999999999999, 29999999999999999999
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OFFSET

1,1


LINKS

Michel Lagneau, Michael De Vlieger and Robert G. Wilson v, Table of n, a(n) for n = 1..1225


MATHEMATICA

f[n_] := Block[{k = 0, p = {}, r = (10^n  1), s = Range@ 10  10}, While[k < n  0, AppendTo[p, Select[r + 10^k*s, PrimeQ]]; k++]; p = Min@ Flatten@ p]; Array[f, 20]


PROG

(PARI) a(n)=my(t=10^n1, p); forstep(d=n1, 0, 1, forstep(k=8, 1, 1, p=t10^d*k; if(ispseudoprime(p), return(p)))); 1 \\ Charles R Greathouse IV, Mar 21 2016


CROSSREFS

Cf. A037071, A241100, A268702  A268706, A241206, A266148.
Sequence in context: A218117 A145104 A114016 * A037071 A126039 A091852
Adjacent sequences: A268704 A268705 A268706 * A268708 A268709 A268710


KEYWORD

nonn,base


AUTHOR

Michel Lagneau, Michael De Vlieger and Robert G. Wilson v, Feb 11 2016


STATUS

approved



