OFFSET
0,4
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
M. Dairyko, S. Tyner, L. Pudwell and C. Wynn, Non-contiguous pattern avoidance in binary trees, 2012, arXiv:1203.0795 [math.CO], p. 17 (Class D).
Michael Dairyko, Lara Pudwell, Samantha Tyner, Casey Wynn, Non-contiguous pattern avoidance in binary trees. Electron. J. Combin. 19 (2012), no. 3, Paper 22, 21 pp. MR2967227.
Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).
FORMULA
G.f.: x*(1-5*x+11*x^2-12*x^3+7*x^4-2*x^5+x^6)/(1-x)^6.
a(n) = (n-1)*(n^4-14*n^3+111*n^2-354*n+480)/120 for n>1. - Bruno Berselli, Feb 06 2013
MATHEMATICA
CoefficientList[Series[(x - 5 x^2 + 11 x^3 - 12 x^4 + 7 x^5 - 2 x^6 + x^7) / (1 - 6 x + 15 x^2 - 20 x^3 + 15 x^4 - 6 x^5 + x^6), {x, 0, 40}], x] (* Vincenzo Librandi, Jun 19 2013 *)
LinearRecurrence[{6, -15, 20, -15, 6, -1}, {0, 1, 1, 2, 5, 12, 26, 52}, 60] (* Harvey P. Dale, May 07 2018 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Feb 01 2013
STATUS
approved