OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Anders Claesson, Mark Dukes and Martina Kubitzke, Partition and composition matrices, arXiv:1006.1312 [math.CO], 2010-2011.
R. Smith and V. Vatter, The enumeration of permutations sortable by pop stacks in parallel, Information Processing Letters, Volume 109, Issue 12, 31 May 2009, Pages 626-629.
Index entries for linear recurrences with constant coefficients, signature (6,-10,6)
FORMULA
G.f.: -x*(2*x-1)^2 / ( -1+6*x-10*x^2+6*x^3 ).
a(n) = 6*a(n-1) - 10*a(n-2) + 6*a(n-3) for n>3. - Colin Barker, Oct 31 2017
MATHEMATICA
LinearRecurrence[{6, -10, 6}, {1, 2, 6}, 30] (* Harvey P. Dale, Oct 12 2023 *)
PROG
(PARI) Vec(x*(1 - 2*x)^2 / (1 - 6*x + 10*x^2 - 6*x^3) + O(x^30)) \\ Colin Barker, Oct 31 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincent Vatter, Aug 29 2009
STATUS
approved