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Search: id:A073122
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| A073122 |
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Minimal reversing binary representation of n. Converting sum of powers of 2 in binary representation of a(n) to alternating sum gives n. See A072339. |
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+0
3
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| 1, 2, 5, 4, 13, 10, 9, 8, 25, 26, 29, 20, 21, 18, 17, 16, 49, 50, 53, 52, 61, 58, 57, 40, 41, 42, 45, 36, 37, 34, 33, 32, 97, 98, 101, 100, 109, 106, 105, 104, 121, 122, 125, 116, 117, 114, 113, 80, 81, 82, 85, 84, 93, 90, 89, 72, 73, 74, 77, 68, 69, 66, 65, 64, 193
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The minimal representation is unique. The number of powers of 2 can be either even or odd. Compare with A065621, in which the number of powers of 2 is odd. The Mathematica program computes the representation for numbers 1 to 2^m. a(0) = 0.
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REFERENCES
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D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, 1981, Vol. 2 (Second Edition), p. 196, (exercise 4.1. Nr. 27)
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FORMULA
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a(2n) = a(n).
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EXAMPLE
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a(11) = 29 because 29 = 16 + 8 + 4 + 1 and 16 - 8 + 4 - 1 = 11.
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MATHEMATICA
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Needs["DiscreteMath`Combinatorica`"]; sumit[s_List] := Module[{i, ss=0}, Do[If[OddQ[i], ss+=s[[ -i]], ss-=s[[ -i]]], {i, Length[s]}]; ss]; m=7; powers=Table[2^i, {i, 0, m}]; lst=Table[2m, {2^m}]; lst2=Table[0, {2^m}]; Do[t=NthSubset[i, powers]; len=Length[t]; st=sumit[t]; If[len<lst[[st]], lst[[st]]=len; lst2[[st]]=Plus@@t], {i, 2^(m+1)-1}]; lst2
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CROSSREFS
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Cf. A065621, A072219, A072339.
Sequence in context: A126356 A121274 A111681 this_sequence A084410 A080067 A117824
Adjacent sequences: A073119 A073120 A073121 this_sequence A073123 A073124 A073125
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KEYWORD
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easy,nice,nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Jul 17 2002
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