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A274005
Number of length-n binary sequences where the sum of each subblock differs by at most 2 from every other subblock of the same length.
4
1, 2, 4, 8, 16, 32, 62, 120, 222, 410, 728, 1294, 2220, 3816, 6380, 10690, 17486, 28704, 46180, 74464, 118226, 188158, 295062, 464146, 721500, 1123384, 1731646, 2676538, 4094776, 6279380, 9562698, 14563312, 22043302, 33433502, 50357062, 75988618, 114092544
OFFSET
0,2
EXAMPLE
For n = 6, the strings 000111 and 111000 are not counted, since the sum of length-3 subblocks that begin and end differ by 3.
MAPLE
A274005 := proc(n)
local a, b, lbdgs, bdgs, i, j, wrks, stri ;
a := 0 ;
for b from 0 to 2^n-1 do
bdgs := convert(b, base, 2) ;
lbdgs := nops(bdgs) ;
bdgs := [op(bdgs), seq(0, i=1..n-lbdgs)] ;
wrks := true;
for stri from 3 to n/2 do
for i from 1 to n-stri do
for j from i+1 to n-stri+1 do
wrks := false;
end if ;
if not wrks then
break;
end if;
end do:
end do:
if not wrks then
break;
end if;
end do ;
if wrks then
a := a+1 ;
end if;
end do:
a ;
end proc: # R. J. Mathar, Jun 16 2016
PROG
CROSSREFS
Cf. A005598, which is the analogous sequence where "2" is replaced by "1".
Cf. A362063.
Sequence in context: A248847 A059173 A355520 * A027560 A135493 A216241
KEYWORD
nonn
AUTHOR
Jeffrey Shallit, Jun 06 2016
EXTENSIONS
More terms from Rémy Sigrist, Jun 24 2021
STATUS
approved

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Last modified September 20 16:06 EDT 2024. Contains 376074 sequences. (Running on oeis4.)