The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A059905 Index of first half of decomposition of integers into pairs based on A000695. 28
 0, 1, 0, 1, 2, 3, 2, 3, 0, 1, 0, 1, 2, 3, 2, 3, 4, 5, 4, 5, 6, 7, 6, 7, 4, 5, 4, 5, 6, 7, 6, 7, 0, 1, 0, 1, 2, 3, 2, 3, 0, 1, 0, 1, 2, 3, 2, 3, 4, 5, 4, 5, 6, 7, 6, 7, 4, 5, 4, 5, 6, 7, 6, 7, 8, 9, 8, 9, 10, 11, 10, 11, 8, 9, 8, 9, 10, 11, 10, 11, 12, 13, 12, 13, 14, 15, 14, 15, 12, 13, 12, 13, 14 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS One coordinate of a recursive non-self-intersecting walk on the square lattice Z^2. LINKS Peter Kagey, Table of n, a(n) for n = 0..8192 G. M. Morton, A Computer Oriented Geodetic Data Base; and a New Technique in File Sequencing, IBM, 1966, with a(n) being section 5.1 step (c). FORMULA n = A000695(a(n)) + 2*A000695(A059906(n)). To get a(n), write n as Sum b_j*2^j, then a(n) = Sum b_(2j)*2^j. - Vladimir Shevelev, Nov 13 2008 a(n) = Sum_{k>=0} A030308(n,k)*A077957(k). - Philippe Deléham, Oct 18 2011 G.f.: (1-x)^(-1) * Sum_{j>=0} 2^j*x^(2^j)/(1+x^(2^j)). - Robert Israel, Aug 12 2015 a(n) = A059906(2*n). - Velin Yanev, Dec 01 2016 EXAMPLE A000695(a(14)) + 2*A000695(A059906(14)) = A000695(2) + 2*A000695(3) = 4 + 2*5 = 14. If n=27, then b_0=1, b_1=1, b_2=0, b_3=1, b_4=1. Therefore a(27) = b_0 + b_2*2 + b_4*2^2 = 5. - Vladimir Shevelev, Nov 13 2008 MAPLE f:= proc(n) local L; L:= convert(n, base, 2); add(L[2*i+1]*2^i, i=0..floor((nops(L)-1)/2)) end; map(f, [\$0..256]); # Robert Israel, Aug 12 2015 MATHEMATICA a[n_] := Module[{P}, (P = Partition[IntegerDigits[2n, 2]//Reverse, 2][[All, 2]]).(2^(Range[Length[P]]-1))]; Array[a, 100, 0] (* Jean-François Alcover, Apr 24 2019 *) PROG (Ruby) def a(n)   (0..n.bit_length/2).to_a.map { |i| (n >> 2 * i & 1) << i}.reduce(:+) end # Peter Kagey, Aug 12 2015 (Python) def a(n): return sum([(n>>2*i&1)<0, s += (n%2)*t; n \= 4; t *= 2); (s); }; \\ Antti Karttunen, Apr 14 2018 CROSSREFS Cf. A000695, A030308, A059906, A057300, A077957. Sequence in context: A105436 A266911 A244075 * A295301 A308133 A306426 Adjacent sequences:  A059902 A059903 A059904 * A059906 A059907 A059908 KEYWORD easy,nonn,look,changed AUTHOR Marc LeBrun, Feb 07 2001 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 6 12:26 EDT 2022. Contains 355110 sequences. (Running on oeis4.)