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 A065845 Let u be any string of n digits from {0,...,3}; let f(u) = number of distinct primes, not beginning with 0, formed by permuting the digits of u; then a(n) = max_u f(u). 10
 1, 2, 3, 6, 13, 36, 96, 253, 765, 2683, 7385, 25075, 83150, 293063, 888689, 3161645, 11097301, 40328876 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE a(2)=2 because 13 and 31 (written in base 4) are primes (7 and 13). MAPLE A065845 := proc(n)     local b, u, udgs, uperm, a;     b :=4 ;     a := 0 ;     for u from b^(n-1) to b^n-1 do         udgs := convert(u, base, b) ;         prs := {} ;         for uperm in combinat[permute](udgs) do             if op(-1, uperm) <> 0 then                 p := add( op(i, uperm)*b^(i-1), i=1..nops(uperm)) ;                 if isprime(p) then                     prs := prs union {p} ;                 end if;             end if;         end do:         a := max(a, nops(prs)) ;     end do:     a ; end proc: for n from 1 do     print(n, A065845(n)) ; end do: # R. J. Mathar, Apr 23 2016 MATHEMATICA c[x_] := Module[{},    Length[Select[Permutations[x],      First[#] != 0 && PrimeQ[FromDigits[#, 4]] &]]]; A065845[n_] := Module[{i},    Return[Max[Map[c, DeleteDuplicatesBy[Tuples[Range[0, 3], n],        Table[Count[#, i], {i, 0, 3}] &]]]]]; Table[A065845[n], {n, 1, 10}] (* Robert Price, Mar 30 2019 *) CROSSREFS Cf. A065843, A065844, A065846, A065847, A065848, A065849, A065850, A065851, A065852, A065853 Sequence in context: A171878 A117403 A002877 * A137273 A135967 A290248 Adjacent sequences:  A065842 A065843 A065844 * A065846 A065847 A065848 KEYWORD base,more,nonn AUTHOR Sascha Kurz, Nov 24 2001 EXTENSIONS 3 more terms from Sean A. Irvine, Sep 06 2009 Definition corrected by David A. Corneth, Apr 23 2016 STATUS approved

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Last modified May 11 18:21 EDT 2021. Contains 343808 sequences. (Running on oeis4.)