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.
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
Keywords
Examples
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.
Links
- Rémy Sigrist, PARI program for A274005
Programs
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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 if abs(add(bdgs[u],u=i..i+stri-1) - add(bdgs[u],u=j..j+stri-1)) >2 then 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
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PARI
See Links section.
Extensions
More terms from Rémy Sigrist, Jun 24 2021