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

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A007175 Number of simplicial 4-clusters with n cells.
(Formerly M2762)
2
1, 1, 1, 3, 8, 40, 211, 1406, 9754, 71591, 537699, 4131943, 32271490, 255690412, 2050376883, 16616721067, 135920429975, 1120999363012, 9313779465810, 77897862860818, 655433405297407, 5544948758579214, 47143948331898873, 402655164736641843, 3453509765971944236, 29734988097830504532 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Hering article has error in the 20th term. - Robert A. Russell, Apr 20 2012

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..26.

F. Hering et al., The enumeration of stack polytopes and simplicial clusters, Discrete Math., 40 (1982), 203-217.

MATHEMATICA

Table[Binomial[4 n, n]/(12 (3 n + 1) (3 n + 2)) +

  If[EvenQ[n],

   Binomial[2 n, n/2]/(8 (3 n/2 + 1)) +

    Binomial[2 n - 1, n/2 - 1]/((3 n/2 + 1)),

   Binomial[2 n - 1, n/2 - 1/2]/(2 (3 n/2 + 1/2))] +

  Switch[Mod[n, 3], 0, Binomial[4 n/3, n/3]/(3 (n + 1)), 1,

   2 Binomial[4 n/3 - 1/3, n/3 - 1/3]/(3 (n + 1)), 2,

   Binomial[4 n/3 - 2/3, n/3 - 2/3]/(n + 1)] +

  If[2 == Mod[n, 4], Binomial[n - 1, n/4 - 1/2]/(2 (3 n/4 + 1/2)), 0] +

  If[1 == Mod[n, 5], 2 Binomial[4 n/5 - 4/5, n/5 - 1/5]/(5 (3 n/5 + 2/5)),

   0], {n, 1, 30}] (* Robert A. Russell, Apr 20 2012 *)

CROSSREFS

Sequence in context: A262126 A110561 A107991 * A152394 A168468 A330527

Adjacent sequences:  A007172 A007173 A007174 * A007176 A007177 A007178

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Robert A. Russell, Apr 20 2012

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 November 28 02:22 EST 2020. Contains 338699 sequences. (Running on oeis4.)