login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A194021 Number of ways to arrange 4 points on an n X n X n triangular grid on an isosceles triangle so that it balances at the midpoint of its central altitude. 1
0, 0, 1, 8, 26, 75, 182, 387, 756, 1382, 2379, 3915, 6198, 9486, 14110, 20475, 29054, 40437, 55309, 74466, 98850, 129548, 167784, 214986, 272758, 342900, 427453, 528698, 649148, 791631, 959254, 1155429, 1383930, 1648890, 1954791, 2306565 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Column 4 of A194024.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 3*a(n-1) - 2*a(n-2) - 2*a(n-4) + 5*a(n-6) - 3*a(n-7) + 3*a(n-8) - 5*a(n-9) + 2*a(n-11) + 2*a(n-13) - 3*a(n-14) + a(n-15).

Empirical g.f.: x^3*(1 + 5*x + 4*x^2 + 13*x^3 + 11*x^4 + 7*x^5 + 6*x^6 + x^7) / ((1 - x)^7*(1 + x)^2*(1 + x^2)*(1 + x + x^2)^2). - Colin Barker, May 05 2018

EXAMPLE

Some solutions for 5 X 5 X 5:

......1..........1..........1..........1..........0..........0..........0

.....0.0........0.0........1.0........0.0........1.1........1.1........0.1

....0.1.1......1.0.0......0.0.0......1.1.0......0.0.1......0.0.0......1.1.0

...0.0.0.0....0.1.0.1....0.1.0.0....0.0.0.0....0.0.0.0....0.1.1.0....0.0.1.0

..0.1.0.0.0..0.0.0.0.0..0.0.0.1.0..0.0.0.1.0..0.1.0.0.0..0.0.0.0.0..0.0.0.0.0

CROSSREFS

Cf. A194024.

Sequence in context: A051669 A207101 A027004 * A245126 A278769 A173365

Adjacent sequences:  A194018 A194019 A194020 * A194022 A194023 A194024

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 12 2011

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 January 22 18:53 EST 2019. Contains 319365 sequences. (Running on oeis4.)