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Write n in binary, interpret that as a decimal number, convert back to binary.
2

%I #4 Mar 30 2012 18:50:24

%S 0,1,1010,1011,1100100,1100101,1101110,1101111,1111101000,1111101001,

%T 1111110010,1111110011,10001001100,10001001101,10001010110,

%U 10001010111,10011100010000,10011100010001,10011100011010,10011100011011

%N Write n in binary, interpret that as a decimal number, convert back to binary.

%F a(n)=A007088(A007088(n)).

%e n=13: [13]D = [1101]B ==> [1101]D = [10001001101]B = a(13).

%t Table[ FromDigits[ IntegerDigits[ FromDigits[ IntegerDigits[n, 2]], 2]], {n, 1, 20}]

%o (PARI) a(n)=subst(Pol(binary(subst(Pol(binary(n)),x,10))),x,10)

%Y Cf. A007088.

%K nonn,base

%O 0,3

%A _Reinhard Zumkeller_, Jun 18 2002