OFFSET
1,2
COMMENTS
From Table 1, p.24, of Feretic. By level 0 cheesy polyominoes, and so too by level 0 polyominoes with cheesy blocks, Feretic appears to mean the usual column-convex polyominoes (A059716). See the paper for his definition.
LINKS
Ray Chandler, Table of n, a(n) for n = 1..100
Svjetlan Feretic, Polyominoes with nearly convex columns: A model with semidirected blocks, Math. Commun. 15 (2010), 77--97, arXiv:0910.4780v1 [math.CO].
Wikipedia, Polyhex
Index entries for linear recurrences with constant coefficients, signature (16, -107, 391, -850, 1108, -797, 169, 266, -317, -159, 913, -1081, 672, -446, 268, -7, 158, -404, 222, -42, 70, -34).
FORMULA
G.f.: (x*(1 - 13*x + 70*x^2 - 202*x^3 + 336*x^4 - 317*x^5 + 143*x^6 + 18*x^7 - 84*x^8 + 11*x^9 + 227*x^10 - 375*x^11 + 267*x^12 - 165*x^13 + 134*x^14 - 21*x^15 + 4*x^16 - 124*x^17 + 98*x^18 - 12*x^19 + 28*x^20 - 16*x^21)) / (1 - 16*x + 107*x^2 - 391*x^3 + 850*x^4 - 1108*x^5 + 797*x^6 - 169*x^7 - 266*x^8 + 317*x^9 + 159*x^10 - 913*x^11 + 1081*x^12 - 672*x^13 + 446*x^14 - 268*x^15 + 7*x^16 - 158*x^17 + 404*x^18 - 222*x^19 + 42*x^20 - 70*x^21 + 34*x^22).
MATHEMATICA
LinearRecurrence[{16, -107, 391, -850, 1108, -797, 169, 266, -317, -159, 913, -1081, 672, -446, 268, -7, 158, -404, 222, -42, 70, -34}, {1, 3, 11, 44, 186, 810, 3582, 15952, 71242, 318441, 1423411, 6360809, 28415254, 126900911, 566604462, 2529439891, 11290673434, 50394458326, 224918228462, 1003813933351, 4479953995624, 19993503244811}, 24] (* Ray Chandler, Jul 16 2015 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jonathan Vos Post, Oct 26 2009
EXTENSIONS
Edited by Ralf Stephan, Feb 07 2014
Extended by Ray Chandler, Jul 16 2015
STATUS
approved