login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A241230 Number of obtuse isosceles triangles on a centered hexagonal grid of size n. 2
0, 12, 108, 528, 1674, 4104, 8622, 16206, 28332, 46200, 71484, 106746, 153552, 214860, 293166, 391470, 512592, 660546, 840840, 1054704, 1308696, 1606776 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

LINKS

Table of n, a(n) for n=1..22.

Eric Weisstein's World of Mathematics, Hex Number.

Eric Weisstein's World of Mathematics, Obtuse Triangle.

Eric Weisstein's World of Mathematics, Isosceles Triangle.

FORMULA

a(n) = A241228(n) - A241229(n).

CROSSREFS

Cf. A190318.

Sequence in context: A271559 A154671 A321672 * A037972 A111990 A053469

Adjacent sequences:  A241227 A241228 A241229 * A241231 A241232 A241233

KEYWORD

nonn,more

AUTHOR

Martin Renner, Apr 17 2014

EXTENSIONS

a(7) from Martin Renner, May 31 2014

a(8)-a(22) from Giovanni Resta, May 31 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 30 23:58 EDT 2020. Contains 334747 sequences. (Running on oeis4.)