login
Gray code variant of A147582.
2

%I #13 Apr 23 2013 02:17:22

%S 1,4,12,4,12,36,12,4,12,36,108,36,12,36,12,4,12,36,108,36,108,324,108,

%T 36,12,36,108,36,12,36,12,4,12,36,108,36,108,324,108,36,108,324,972,

%U 324,108,324,108,36,12,36,108,36,108,324,108,36,12,36,108

%N Gray code variant of A147582.

%C A147582 is generated by using the binary weight of n, A000120 = wt().

%C Here instead, A224512 uses the Gray code weight, A005811 = gt().

%F a(1) = 1. For a(n)>1, a(n) = 4 * 3^(gt(n-1)-1).

%e A003188(5-1) = 6 = 110 (base 2), so gt(5-1) = 2. Then a(5) = 12 = 4 * 3^1 = 12.

%o (PARI) gt(n) = sum(kk=1, n, (-1)^((kk/2^valuation(kk, 2)-1)/2)); \\ from A005811.

%o a(n) = if (n==1, 1, 4 * 3^(gt(n-1)-1)); \\ _Michel Marcus_, Apr 22 2013

%Y Cf. A147582, A224513.

%K nonn

%O 1,2

%A _Gary W. Adamson_, Apr 08 2013