A207670 - OEIS

%I #7 Aug 19 2021 10:56:38

%S 1,2,9,11,12,13,15,16,18,19,21,23,24,26,27,28,29,30,31,32,33,36,37,39,

%T 40,42,44,45,47,48,50,51,52,54,55,56,57,60,61,62,63,64,66,68,69,70,72,

%U 74,75,76,78,80,81,82,83,84,85,87,88,90,91,93,95,96,98,99,100

%N Numbers that match polynomials with coefficients in {0,1,2} that are not irreducible modulo 3; complement of A207670.

%C See the Comments at A207669.

%e (See the Example section of A207669.)

%t t = Table[IntegerDigits[n, 3], {n, 1, 1000}];

%t b[n_] := Reverse[Table[x^k, {k, 0, n}]]

%t p[n_, x_] := t[[n]].b[-1 + Length[t[[n]]]]

%t Table[p[n, x], {n, 1, 15}]

%t u = {}; Do[n++;

%t If[IrreduciblePolynomialQ[p[n, x], Modulus -> 3],

%t   AppendTo[u, n]], {n, 1, 400}]

%t u                           (* A207669 *)

%t Complement[Range[200], %]   (* A207670 *)

%t b[n_] := FromDigits[IntegerDigits[u, 3][[n]]]

%t Table[b[n], {n, 1, 50}]     (* A207671 *)

%Y Cf. A207669.

%K nonn

%O 1,2

%A _Clark Kimberling_, Feb 26 2012