cp's OEIS Frontend

A115873 First column of A115872.

%I A115873 #7 Jan 04 2022 18:35:24
%S A115873 1,1,3,1,7,3,7,1,15,7,3,3,5,7,15,1,31,15,7,7,31,3,7,3,31,5,31,7,31,15,
%T A115873 31,1,63,31,15,15,7,7,7,7,63,31,3,3,63,7,15,3,21,31,63,5,63,31,7,7,9,
%U A115873 31,63,15,21,31,63,1,127,63,31,31,15,15,15,15,127,7,31,7,15,7,15,7,51
%N A115873 First column of A115872.
%F A115873 a(2^k) = 1, a(2n) = a(n).
%t A115873 X[a_, b_] := Module[{A, B, C, x},
%t A115873    A = Reverse@IntegerDigits[a, 2];
%t A115873    B = Reverse@IntegerDigits[b, 2];
%t A115873    C = Expand[
%t A115873       Sum[A[[i]]*x^(i - 1), {i, 1, Length[A]}]*
%t A115873       Sum[B[[i]]*x^(i - 1), {i, 1, Length[B]}]];
%t A115873    PolynomialMod[C, 2] /. x -> 2];
%t A115873 T[n_, k_] := Module[{x = BitXor[n - 1, 2 n - 1], k0 = k},
%t A115873      For[i = 1, True, i++, If[n*i == X[x, i],
%t A115873      If[k0 == 1, Return[i], k0--]]]];
%t A115873 a[n_] := T[n, 1];
%t A115873 Table[a[n], {n, 1, 100}] (* _Jean-François Alcover_, Jan 04 2022 *)
%Y A115873 Cf. A114395, A114396, A115872.
%K A115873 nonn
%O A115873 1,3
%A A115873 _Antti Karttunen_, Feb 07 2006