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Positive numbers that are not the sum of two nonprime squarefree numbers (A000469).
1

%I #9 Jul 21 2017 05:32:21

%S 1,3,4,5,6,8,9,10,13,14,17,18,19,26,33,38,46,62,82

%N Positive numbers that are not the sum of two nonprime squarefree numbers (A000469).

%C The sequence is conjectured to be complete.

%t nmax = 82; f[x_] := Sum[Boole[SquareFreeQ[k] && PrimeNu[k] != 1] x^k, {k, 1, nmax}]^2; b = Exponent[#, x] & /@ List @@ Normal[Series[f[x], {x, 0, nmax}]]; c = Complement[Range[nmax], b][[1 ;; 19]]

%Y Cf. A000469, A014092, A071068, A071331, A098235, A239508, A239509.

%K nonn,more

%O 1,2

%A _Ilya Gutkovskiy_, Jul 20 2017