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 A091247 Characteristic function of A091242: 1 if the n-th GF(2)[X] polynomial is reducible, 0 otherwise. 78

%I

%S 0,0,0,0,1,1,1,0,1,1,1,0,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,1,

%T 1,1,1,0,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,1,1,0,1,1,1,0,1,0,1,1,1,1,1,0,

%U 1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,1,1,0,1,1,1,1

%N Characteristic function of A091242: 1 if the n-th GF(2)[X] polynomial is reducible, 0 otherwise.

%H A. Karttunen, <a href="/A091247/a091247.scm.txt">Scheme-program for computing this sequence.</a>

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>

%H <a href="/index/Ge#GF2X">Index entries for sequences operating on GF(2)[X]-polynomials</a>

%F a(n) = A066247(A091203(n)) = A066247(A091205(n)).

%o (PARI) a(n) = if (n<2, 0, ! polisirreducible(Mod(1,2)*Pol(binary(n)))); \\ _Michel Marcus_, Apr 12 2015

%Y Cf. A066247, A091203, A091205, A091246.

%Y Complementary to A091225. Partial sums give A091245.

%K nonn

%O 0,1

%A _Antti Karttunen_, Jan 03 2004

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Last modified September 20 06:51 EDT 2020. Contains 337264 sequences. (Running on oeis4.)