OFFSET
0,3
LINKS
A. Bernini, F. Disanto, R. Pinzani and S. Rinaldi, Permutations defining convex permutominoes, J. Int. Seq. 10 (2007) # 07.9.7. [See S_{n+1}.]
F. Disanto and S. Rinaldi, Symmetric convex permutominoes and involutions, PU. M. A., Vol. 22 (2011), No. 1, pp. 39-60. - From N. J. A. Sloane, May 04 2012
FORMULA
Conjecture: -(n-1)*(3*n^2-27*n+56)*a(n) +2*(n-5)*(3*n^2-12*n+5)*a(n-1) +4*(3*n^3-33*n^2+110*n-118)*a(n-2) -8*(n-3)*(3*n^2-21*n+32)*a(n-3)=0. - R. J. Mathar, Jan 04 2017
MATHEMATICA
Join[{1}, Table[((n+3)2^(n-2))-(n Binomial[n-1, Floor[(n-1)/2]]) -((n-1)Binomial[n-2, Floor[(n-2)/2]]), {n, 50}]] (* Harvey P. Dale, Mar 17 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jul 28 2007
STATUS
approved