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A099896
A permutation of the natural numbers where a(n) = n XOR [n/2] XOR [n/4].
5
1, 3, 2, 7, 6, 4, 5, 14, 15, 13, 12, 9, 8, 10, 11, 28, 29, 31, 30, 27, 26, 24, 25, 18, 19, 17, 16, 21, 20, 22, 23, 56, 57, 59, 58, 63, 62, 60, 61, 54, 55, 53, 52, 49, 48, 50, 51, 36, 37, 39, 38, 35, 34, 32, 33, 42, 43, 41, 40, 45, 44, 46, 47, 112, 113, 115, 114, 119, 118, 116
OFFSET
1,2
COMMENTS
Related to Gray code numbers (A003188) since A003188(n) = n XOR [n/2].
Inverse: A100280; A100281(n) = a(a(n)). - Reinhard Zumkeller, Nov 11 2004
FORMULA
XOR BINOMIAL transform begins: B={1, 2, 3, 7, 7, 0, 0, 14, 14, 0, 0, ...} and continues with B(2^k)=B(2^k+1)=7*2^(k-2) (for k>=2) and zeros elsewhere.
MATHEMATICA
Array[BitXor[BitXor[#, Floor[#/2]], Floor[#/4]]&, 70] (* Harvey P. Dale, Aug 10 2012 *)
PROG
(PARI) a(n)=bitxor(bitxor(n, n\2), n\4)
CROSSREFS
Sequence in context: A340447 A360983 A154448 * A160679 A335536 A233276
KEYWORD
nonn,look
AUTHOR
Paul D. Hanna, Nov 09 2004
STATUS
approved