OFFSET
1,4
COMMENTS
The maximum number of I patterns tetrominos that can be packed into an n X n array of squares with rotation is prohibited.
u(n) = n*(n mod 4), where u(n) is total number of squares left after packing I patterns into n X n squares.
a(n) = A132028(n) for 4 <= n <= 31.
LINKS
Kival Ngaokrajang, Illustration of initial terms
Wikipedia, Tetromino
Index entries for linear recurrences with constant coefficients, signature (1,0,0,2,-2,0,0,-1,1).
FORMULA
a(n) = (n^2 - n*(n mod 4))/4.
G.f.: (x^7 + x^6 + x^5 + x^4 + 4*x^3)/((1-x)*(1-x^4)^2). - Ralf Stephan, Dec 08 2013
MATHEMATICA
Table[n*Floor[n/4], {n, 80}] (* or *) LinearRecurrence[{1, 0, 0, 2, -2, 0, 0, -1, 1}, {0, 0, 0, 4, 5, 6, 7, 16, 18}, 80] (* Harvey P. Dale, Aug 22 2020 *)
PROG
(Small Basic)
For n = 1 To 100
a = (n*n - n*math.Remainder(n, 4))/4
TextWindow.Write(a+", ")
EndFor
(PARI) a(n) = n * floor(n/4); \\ Joerg Arndt, Dec 08 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Kival Ngaokrajang, Dec 03 2013
STATUS
approved