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%I #28 Aug 02 2022 09:31:45
%S 19,199,1999,49999,199999,2999999,19999999,799999999,10999999999,
%T 59999999999,1099999999999,34999999999999,59999999999999,
%U 499999999999999,14999999999999999,139999999999999999
%N Smallest prime ending in exactly n 9's.
%C From _Jeppe Stig Nielsen_, Jul 30 2022: (Start)
%C Can decrease, for example a(25) < a(24). So not the same as Smallest prime ending in n or more 9s.
%C a(n) can contain other 9s as well, for example a(46), a(118), a(156). (End)
%H Hugo Pfoertner, <a href="/A065582/b065582.txt">Table of n, a(n) for n = 1..500</a> (first 100 terms from Harry J. Smith).
%t 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} ]
%t 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 *)
%o (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
%o (Python)
%o from sympy import isprime
%o def a(n):
%o pow, end, i = 10**n, 10**n-1, 1
%o while i%10 == 9 or not isprime(i*pow + end): i += 1
%o return i*pow + end
%o print([a(n) for n in range(1, 20)]) # _Michael S. Branicky_, Jul 30 2022
%Y Cf. A037071, A065592, A065821, A065580, A065581.
%K nonn,base
%O 1,1
%A _Robert G. Wilson v_, Nov 28 2001
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