cp's OEIS Frontend

A065850 Let u be any string of n digits from {0,...,8}; let f(u) = number of distinct primes, not beginning with 0, formed by permuting the digits of u to a base-9 number; then a(n) = max_u f(u).

%I A065850 #31 Jul 09 2024 23:25:20
%S A065850 1,2,5,11,39,161,865,4604,22636,161107,840691,4813328,29664164
%N A065850 Let u be any string of n digits from {0,...,8}; let f(u) = number of distinct primes, not beginning with 0, formed by permuting the digits of u to a base-9 number; then a(n) = max_u f(u).
%e A065850 a(2)=2 because 12 and 21 (written in base 9) are primes (11 and 19).
%t A065850 c[x_] := Module[{},
%t A065850    Length[Select[Permutations[x],
%t A065850      First[#] != 0 && PrimeQ[FromDigits[#, 9]] &]]];
%t A065850 A065850[n_] := Module[{i},
%t A065850    Return[Max[Map[c, DeleteDuplicatesBy[Tuples[Range[0, 8], n],
%t A065850        Table[Count[#, i], {i, 0, 8}] &]]]]];
%t A065850 Table[A065850[n], {n, 1, 7}] (* _Robert Price_, Mar 30 2019 *)
%Y A065850 Cf. A065843, A065844, A065845, A065846, A065847, A065848, A065849, A065851, A065852, A065853.
%K A065850 base,more,nonn
%O A065850 1,2
%A A065850 _Sascha Kurz_, Nov 24 2001
%E A065850 a(10)-a(11) from _Sean A. Irvine_, Sep 06 2009
%E A065850 Definition corrected by _David A. Corneth_, Apr 23 2016
%E A065850 a(12) from _Michael S. Branicky_, Jul 03 2024
%E A065850 a(13) from _Michael S. Branicky_, Jul 09 2024