OFFSET
1,2
COMMENTS
The sequence would be a concatenation of chunks of the form {x, 0, 0}, where x is a value greater than zero, apart from the first term. Here only x's are listed.
EXAMPLE
a(2) = 4 because for the first 4 numbers {1,2,3,4} we have 1423, 2143, 2341, 4231 that are prime.
MAPLE
with(combinat): P:=proc(q) local a, b, j, k, n, t; a:=[];
for n from 1 to q do a:=permute(3*n-2); t:=0;
for k from 1 to nops(a) do b:=0;
for j from 1 to nops(a[k]) do b:=10^(ilog10(a[k][j])+1)*b+a[k][j]; od;
if isprime(b) then t:=t+1; fi; od; print(t);
od; end: P(5); # Paolo P. Lava, Nov 17 2017
MATHEMATICA
Array[Count[Map[FromDigits@ Flatten[IntegerDigits@ #] &, Permutations[Range@ #, {#}]], _?PrimeQ] &, 10] (* Michael De Vlieger, Nov 17 2017 *)
CROSSREFS
KEYWORD
nonn,base,more,hard
AUTHOR
Paolo P. Lava, Nov 17 2017
EXTENSIONS
a(4)-a(5) from Giovanni Resta, Nov 17 2017
STATUS
approved