OFFSET
1,1
COMMENTS
Column 4 of A255604.
FORMULA
a(n) = floor(6*n^2/(4*tan(Pi/6))), n >= 1.
MATHEMATICA
Table[IntegerPart[(6*n^2/(4*Tan[Pi/6]))], {n, 50}] (* Michael De Vlieger, Mar 18 2015 *)
PROG
(PARI){for(n=1, 100, a=floor(6*n^2/(4*tan(Pi/6))); print1(a, ", "))}
(PARI) a(n) = sqrtint(27*n^4)>>1; \\ Kevin Ryde, May 07 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Kival Ngaokrajang, Feb 27 2015
STATUS
approved