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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A360800 Numbers Sum_{i=1..2r+1} 2^k(i) such that k(1) is even and, for r > 0 and i < 2r+1, the difference k(i+1)-k(i) is > 0 and odd. 1
 1, 4, 7, 16, 19, 25, 28, 31, 64, 67, 73, 76, 79, 97, 100, 103, 112, 115, 121, 124, 127, 256, 259, 265, 268, 271, 289, 292, 295, 304, 307, 313, 316, 319, 385, 388, 391, 400, 403, 409, 412, 415, 448, 451, 457, 460, 463, 481, 484, 487, 496, 499, 505, 508, 511, 1024 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This is a subsequence of A360799. Another description of the terms: in the base-2 representation, the number of ones is odd and all zeros are grouped in blocks of even length. That is why the terms less than 2^(2j+1) describe start profiles for tiling a (2j+1) X m wall with 1 X 2 dominos, see examples and A360799. LINKS Table of n, a(n) for n=1..56. EXAMPLE A 5 X m wall is tiled bottom-up with dominos, start profiles: _ _ _ _ _ _ _ _ _ _ _ _ _ ___ ___| | ___| |___ ___| | | | | |___| | | | | | | | | |___|___|_| |___|_|___| |___|_|_|_| |_|___|_|_| |_|_|_|_|_| 0 0 0 0 1 0 0 1 0 0 0 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1 = a(1) 4 = a(2) 7 = a(3) 19 = a(5) 31 = a(7) also the mirror images of 1 (16), 19 (25) and 7 (28). PROG (Maxima) block(kmax: 100, a:[], oddsum(y):= block(su1:0, su2:0, pold:0, ok: true, while y>0 and ok do(p:mod(y, 2), y:(y-p)/2, if p=1 then(if pold=0 and su2=1 then ok:false, su1:1-su1, su2:0) elseif p=0 then su2:1-su2, pold:p), return(is(ok and su1=1))), for k from 1 thru kmax do if oddsum(k) then a:append(a, [k]), a); CROSSREFS Cf. A001835, A003775, A028469, A028471, A180963, A187616, A360799. Sequence in context: A310928 A018887 A059014 * A255650 A350961 A166700 Adjacent sequences: A360797 A360798 A360799 * A360801 A360802 A360803 KEYWORD nonn AUTHOR Gerhard Kirchner, Feb 24 2023 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 November 30 05:42 EST 2023. Contains 367454 sequences. (Running on oeis4.)