1,3

A centered hexagonal grid of size n is a grid with A003215(n-1) points forming a hexagonal lattice.

Table of n, a(n) for n=1..13.

Eric Weisstein's World of Mathematics, Hex Number.

Eric Weisstein's World of Mathematics, Scalene Triangle.

a(n) = A241231(n) - A241237(n).

For n = 2 the only kind of non-congruent scalene triangles is the following:

/. *

* . *

\. .

Cf. A190313, A241227.

Sequence in context: A086120 A129701 A221746 * A044270 A044651 A287303

Adjacent sequences: A241233 A241234 A241235 * A241237 A241238 A241239

nonn

Martin Renner, Apr 17 2014

a(7) from Martin Renner, May 31 2014

a(8)-a(13) from Giovanni Resta, May 31 2014

approved