OFFSET
3,1
LINKS
Terrel Trotter, Perimeter-Magic Polygons, Journal of Recreational Mathematics Vol. 7, No. 1, 1974, pp. 14-20 (see equations 5 and 7).
FORMULA
O.g.f.: x*(1 + x^2 + y + x*(2 + 3*y))/((1 - x)^3*(1 + x)^2*(1 - y^2)).
E.g.f.: x*((5 + 2*x)*cosh(x + y) - cosh(x - y) + 2*(2 + x)*sinh(x + y))/4.
T(k, n) = k*(1 + k + (n mod 2)*(1 - (k mod 2)))/2.
T(k, 3) = A265225(k-1) (conjectured).
EXAMPLE
The table begins:
k\n| 3 4 5 6 7 ...
---+--------------------
3 | 6 6 6 6 6 ...
4 | 12 10 12 10 12 ...
5 | 15 15 15 15 15 ...
6 | 24 21 24 21 24 ...
7 | 28 28 28 28 28 ...
...
MATHEMATICA
T[k_, n_]:=k(1+k+Mod[n, 2](1-Mod[k, 2]))/2; Table[T[k+3-n, n], {k, 3, 14}, {n, 3, k}]//Flatten
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Stefano Spezia, Apr 03 2021
STATUS
approved