OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..600
Wikipedia, Tromino
FORMULA
G.f.: (-x^14 +45*x^13 -790*x^12 +7195*x^11 -37791*x^10 +120544*x^9 -241021*x^8 +307384*x^7 -251359*x^6 +131039*x^5 -42817*x^4 +8472*x^3 -952*x^2 +53*x -1) / (x^15 -56*x^14 +1223*x^13 -13643*x^12 +87066*x^11 -338409*x^10 +836269*x^9 -1345297*x^8 +1419177*x^7 -976456*x^6 +431092*x^5 -118633*x^4 +19424*x^3 -1761*x^2 +76*x -1).
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Dec 07 2013
STATUS
approved