A027562 Number of 5-unbalanced strings of length n (=2^n-A027560(n)).

0, 0, 0, 0, 0, 0, 2, 6, 24, 62, 178, 426, 1070, 2444, 5720, 12662, 28392, 61464, 133980, 285304, 609750, 1282278, 2701396, 5626046, 11725614, 24234418, 50093914, 102905764, 211350724, 432051438, 882876204, 1797686520

Offset

0,7

Comments

a(n) is also the number of different ways to fold down a folding yardstick with n sticks (stick length is one) to form an equilateral hexagon with side length one. - Frank Hollstein, May 01 2019

Links

Table of n, a(n) for n=0..31.

Index entries for linear recurrences with constant coefficients, signature (3,3,-14,2,15,-6).

Formula

G.f.: 2x^6/[(1-2x)(1-3x^2)(1-x-2x^2+x^3)].

Crossrefs

Cf. A027560.

Sequence in context: A357249 A107762 A253901 * A236625 A096259 A338614

Adjacent sequences: A027559 A027560 A027561 * A027563 A027564 A027565

Keyword

nonn

Author

R. K. Guy, David Callan

Status

approved