OFFSET
0,3
COMMENTS
A permutation is said to be Grassmannian if it has at most one descent. The definition for sigma is a pattern of size 10 with exactly one descent. For example, sigma can be chosen to be 124789356(10), 247913568(10), 36(10)1245789, 57(10)1234689, etc.
LINKS
J. B. Gil and J. Tomasko, Restricted Grassmannian permutations, ECA 2:4 (2022) Article S4PP6.
Index entries for linear recurrences with constant coefficients, signature (10,-45,120,-210,252,-210,120,-45,10,-1).
FORMULA
a(n) = 1 + Sum_{i=2..9} binomial(n,i).
G.f.: (1-9*x+37*x^2-90*x^3+142*x^4-150*x^5+106*x^6-48*x^7+13*x^8-x^9)/(1-x)^10.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jessica A. Tomasko, Apr 29 2023
STATUS
approved