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2

%I #6 Mar 30 2012 18:58:12

%S 1,2,3,4,6,8,9,12,13,15,16,17,18,19,21,24,25,26,27,30,32,33,34,35,36,

%T 38,39,42,43,45,47,48,49,50,51,52,54,60,64,65,66,67,68,70,72,73,76,78,

%U 84,86,90,91,94,96,97,98,99,100,102,104,105,108,117,120,121,128

%N (1/5)A206715.

%C It is conjectured that all the terms of this sequence are integers; this may be equivalent to the conjecture at A131853.

%t t = Table[IntegerDigits[n, 2], {n, 1, 3000}];

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

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

%t TableForm[Table[{n, p[n, x], Factor[p[n, x]]},

%t {n, 1, 16}]]

%t u = {}; Do[n++; If[(p[n, x] /. x -> I) == 0,

%t AppendTo[u, n]], {n, 800}]

%t u (* A206715 *)

%t u/5 (* A206716 *)

%Y Cf. A131853, A206074, A206715.

%K nonn

%O 1,2

%A _Clark Kimberling_, Feb 11 2012