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A102600
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Largest prime which can be formed from digits of n^2, or 0, if no prime.
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1
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0, 0, 0, 61, 5, 3, 0, 0, 0, 0, 211, 41, 691, 691, 5, 5, 829, 43, 631, 0, 41, 0, 59, 67, 5, 67, 97, 487, 41, 0, 691, 4201, 809, 6151, 2521, 691, 9631, 4441, 521, 601, 8161, 761, 8941, 9631, 5, 6211, 2029, 43, 4201, 5, 601, 4027, 8209, 691, 5023, 6133, 439, 6343, 8431, 3
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OFFSET
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1,4
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LINKS
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FORMULA
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EXAMPLE
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a(11)=211 because 211 is the largest prime which can be made from digits of 11*11=121: {1,1,2}.
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MAPLE
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f:= proc(n) local L, N, d, i, j, S, s, p;
L:= convert(n^2, base, 10);
N:= nops(L);
for d from N to 1 by -1 do
S:= sort(combinat:-permute(L, d));
for i from nops(S) to 1 by -1 do
s:= S[i];
p:= add(s[j]*10^(d-j), j=1..d);
if isprime(p) then return p fi
od od;
0
end proc:
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MATHEMATICA
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a[n_]:=Max[0, Select[FromDigits/@Permutations[IntegerDigits[n^2], {1, IntegerLength[n^2]}], PrimeQ]]; Table[a[n], {n, 60}] (* James C. McMahon, Jan 09 2024 *)
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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