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A065582
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Smallest prime ending in exactly n 9's.
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11
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19, 199, 1999, 49999, 199999, 2999999, 19999999, 799999999, 10999999999, 59999999999, 1099999999999, 34999999999999, 59999999999999, 499999999999999, 14999999999999999, 139999999999999999
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OFFSET
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1,1
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COMMENTS
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Can decrease, for example a(25) < a(24). So not the same as Smallest prime ending in n or more 9s.
a(n) can contain other 9s as well, for example a(46), a(118), a(156). (End)
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LINKS
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MATHEMATICA
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Do[a = Table[9, {n} ]; k = 0; While[ b = FromDigits[ Join[ IntegerDigits[k], a]]; Mod[k, 10] == 9 || !PrimeQ[b], k++ ]; Print[b], {n, 1, 17} ]
pe9[n_]:=Module[{k=1, rh=FromDigits[PadRight[{}, n, 9]]}, While[!PrimeQ[ k 10^n+rh], k++]; k 10^n+rh]; Array[pe9, 20] (* Harvey P. Dale, Mar 26 2012 *)
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PROG
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(PARI) { for (n=1, 100, t=10^n; b=t - 1; d=0; while(!isprime(b + t*d), d++; if (d%10==9, d++)); write("b065582.txt", n, " ", b + t*d) ) } \\ Harry J. Smith, Oct 23 2009
(Python)
from sympy import isprime
def a(n):
pow, end, i = 10**n, 10**n-1, 1
while i%10 == 9 or not isprime(i*pow + end): i += 1
return i*pow + end
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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