A102600 Largest prime which can be formed from digits of n^2, or 0, if no prime.

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

Offset

1,4

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

a(n) = A101991(n^2). - Michel Marcus, Oct 05 2013

Example

a(11)=211 because 211 is the largest prime which can be made from digits of 11*11=121: {1,1,2}.

Maple

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:
map(f, [$1..100]); # Robert Israel, Jan 10 2024

Mathematica

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 *)

Crossrefs

Cf. A101991.

Sequence in context: A051322 A345224 A198189 * A316918 A077331 A106426

Adjacent sequences: A102597 A102598 A102599 * A102601 A102602 A102603

Keyword

base,easy,nonn,look

Author

Zak Seidov, Jan 29 2005

Extensions

Data corrected for n={18,33,39,57} by James C. McMahon, Jan 10 2024.

Status

approved