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

 

Logo

The submissions stack has been unacceptably high for several months now. Please voluntarily restrict your submissions and please help with the editing. (We don't want to have to impose further limits.)

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A030653 n^3*a(n) is number of circles in complex projective plane tangent to three smooth curves of degree n in general position. 1
4, 23, 60, 121, 212, 339, 508, 725, 996, 1327, 1724, 2193, 2740, 3371, 4092, 4909, 5828, 6855, 7996, 9257, 10644, 12163, 13820, 15621, 17572, 19679, 21948, 24385, 26996, 29787, 32764, 35933, 39300, 42871, 46652, 50649, 54868, 59315 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

See formula for enumeration of contacts in Fulton-Kleiman-MacPherson (pp. 156-196 of Lect. Notes Math. n.997).

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

FORMULA

a(n)=n^3+3*n^2+3*n-3.

G.f.: x*(4+7*x-8*x^2+3*x^3)/(1-x)^4. [Colin Barker, Sep 03 2012]

MATHEMATICA

LinearRecurrence[{4, -6, 4, -1}, {4, 23, 60, 121}, 40] (* Harvey P. Dale, Nov 29 2014 *)

PROG

(MAGMA) [n^3+3*n^2+3*n-3: n in [1..45]]; // Vincenzo Librandi, Jun 30 2011

CROSSREFS

Sequence in context: A106684 A239624 A179628 * A085505 A065972 A132112

Adjacent sequences:  A030650 A030651 A030652 * A030654 A030655 A030656

KEYWORD

nonn,nice,easy

AUTHOR

Paolo Dominici (pl.dm(AT)libero.it)

STATUS

approved

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

Content is available under The OEIS End-User License Agreement .

Last modified August 27 21:58 EDT 2015. Contains 261098 sequences.