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A083576
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Least n-digit prime star number.
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1
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13, 181, 1093, 10333, 100621, 1040833, 10085473, 100000837, 1000705861, 10003758337, 100012479337, 1000001026513, 10000000794181, 100000078156441, 1000000776555301, 10000014919168441, 100000008716411701
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OFFSET
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2,1
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LINKS
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MAPLE
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f:= proc(n) local i, t, s;
t:= ceil(1/2 + sqrt(3+6*10^(n-1))/6);
for i from t do
s:= 6*i*(i-1)+1;
if isprime(s) then return s fi
od
end proc:
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MATHEMATICA
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With[{psn=Select[Table[6n(n-1)+1, {n, 130*10^6}], PrimeQ]}, Table[ SelectFirst[ psn, IntegerLength[#]==k&], {k, 2, 18}]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 12 2020 *)
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PROG
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(PARI) star(n) = 6*n*(n-1)+1; L(n)=length(Str(n)); { stl(m)=print1(0", "); k=1; for(n=2, m, while(!isprime(star(k)) || L(star(k))!=n, k++); print1(star(k)", ")) }
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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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EXTENSIONS
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STATUS
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approved
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