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A208180 Numbers that match polynomials over {0,1} that have a factor containing -2 as a coefficient; see Comments.

%I A208180 #11 Aug 03 2025 21:05:25
%S A208180 663,669,741,933,1326,1338,1421,1482,1866,2163,2181,2199,2229,2247,
%T A208180 2289,2387,2469,2499,2577,2589,2613,2631,2643,2649,2652,2661,2676,
%U A208180 2679,2757,2769,2842,2949,2964,2973,3115,3129,3237,3241,3297,3395
%N A208180 Numbers that match polynomials over {0,1} that have a factor containing -2 as a coefficient; see Comments.
%C A208180 The polynomials having coefficients in {0,1} are enumerated at A206073. They include the following:
%C A208180 p(1,x) = 1
%C A208180 p(2,x) = x
%C A208180 p(3,x) = x + 1
%C A208180 p(4,x) = x^2
%C A208180 p(663,x) = 1 + x + x^2 + x^4 + x^7 + x^9 = (x + 1)*f(x), where f(x) = 1 + x^2 - x^3 + 2 x^4 - 2 x^5 + 2 x^6 - x^7 + x^8. This show that a factor of p(663,x) has a factor that has -2 as a coefficient. Actually, 663 is the least n for which p(n,x) has a coefficient not in {-1,0,1,2}.
%C A208180 The enumeration scheme for all nonzero polynomials with coefficients in {0,1} is introduced in Comments at A206073. The sequence A206073 itself enumerates only those polynomials that are irreducible over the ring of polynomials having integer coefficients; therefore, A206073 and A208180 are disjoint.
%t A208180 t = Table[IntegerDigits[n, 2], {n, 1, 4000}];
%t A208180 b[n_] := Reverse[Table[x^k, {k, 0, n}]]
%t A208180 p[n_, x_] := p[n, x] = t[[n]].b[-1 + Length[t[[n]]]]
%t A208180 TableForm[Table[{n, p[n, x], Factor[p[n, x]]}, {n, 1, 4000}]];
%t A208180 DeleteCases[
%t A208180 Map[{#[[1]], Cases[#[[2]], {___, -2, ___}]} &,
%t A208180   Map[{#[[1]], CoefficientList[#[[2]], x]} &,
%t A208180    Map[{#[[1]], Map[#[[1]] &, #[[2]]]} &,
%t A208180     Map[{#[[1]], Rest[FactorList[#[[2]]]]} &,
%t A208180      Table[{n, Factor[p[n, x]]}, {n, 1, 3600}]]]]], {_, {}}]
%t A208180 Map[#[[1]] &, %]   (* A208180 *)
%t A208180 (* _Peter J. C. Moses_, Feb 22 2012 *)
%Y A208180 Cf. A208179, A206073, A206284, A208181, A208182.
%K A208180 nonn
%O A208180 1,1
%A A208180 _Clark Kimberling_, Feb 24 2012