cp's OEIS Frontend

A065848 Let u be any string of n digits from {0,...,6}; let f(u) = number of distinct primes, not beginning with 0, formed by permuting the digits of u to a base-7 number; then a(n) = max_u f(u).

%I A065848 #34 Jul 08 2024 10:38:56
%S A065848 1,2,5,15,45,154,674,3575,14946,68308,345653,1931846,9776107,51415223,
%T A065848 311415054
%N A065848 Let u be any string of n digits from {0,...,6}; let f(u) = number of distinct primes, not beginning with 0, formed by permuting the digits of u to a base-7 number; then a(n) = max_u f(u).
%e A065848 a(2)=2 because 14 and 41 (written in base 7) are primes (11 and 29).
%e A065848 a(3)=5 because 124, 142, 214, 241 and 421 (in base 7) are primes (67, 79, 109, 127 and 211). - _R. J. Mathar_, Apr 23 2016
%t A065848 c[x_] := Module[{},
%t A065848    Length[Select[Permutations[x],
%t A065848      First[#] != 0 && PrimeQ[FromDigits[#, 7]] &]]];
%t A065848 A065848[n_] := Module[{i},
%t A065848    Return[Max[Map[c, DeleteDuplicatesBy[Tuples[Range[0, 6], n],
%t A065848        Table[Count[#, i], {i, 0, 6}] &]]]]];
%t A065848 Table[A065848[n], {n, 1, 7}] (* _Robert Price_, Mar 30 2019 *)
%Y A065848 Cf. A065843, A065844, A065845, A065846, A065847, A065849, A065850, A065851, A065852, A065853.
%K A065848 base,more,nonn
%O A065848 1,2
%A A065848 _Sascha Kurz_, Nov 24 2001
%E A065848 2 more terms from _Sean A. Irvine_, Sep 06 2009
%E A065848 Definition corrected by _David A. Corneth_, Apr 23 2016
%E A065848 a(13) from _Michael S. Branicky_, May 28 2024
%E A065848 a(14) from _Michael S. Branicky_, Jun 25 2024
%E A065848 a(15) from _Michael S. Branicky_, Jul 08 2024