OFFSET

0,2

LINKS

Rémy Sigrist, PARI program for A274005

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

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

PROG

(PARI) See Links section.

CROSSREFS

KEYWORD

nonn

AUTHOR

Jeffrey Shallit, Jun 06 2016

EXTENSIONS

More terms from Rémy Sigrist, Jun 24 2021

STATUS

approved