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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A053153 Number of 3-element intersecting families whose union is an n-element set. 2
0, 0, 13, 170, 1605, 13390, 104993, 794010, 5867245, 42681830, 307120473, 2192847250, 15570312485, 110116458270, 776528783953, 5464646634890, 38398786511325, 269529019274710, 1890415785439433, 13251574765596930 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

REFERENCES

V. Jovovic, G. Kilibarda, On the number of Boolean functions in the Post classes F^{mu}_8, Diskretnaya Matematika, 11 (1999), no. 4, 127-138 (translated in Discrete Mathematics and Applications, 9, (1999), no. 6).

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (22,-190,820,-1849,2038,-840).

FORMULA

a(n) = 1/3!*(7^n -3*5^n +3*4^n -4*3^n +3*2^n +2).

G.f. -x^3*(280*x^3 -335*x^2 +116*x -13)/((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)*(7*x-1)). - Colin Barker, Jul 29 2012

MATHEMATICA

LinearRecurrence[{22, -190, 820, -1849, 2038, -840}, {0, 0, 13, 170, 1605, 13390}, 20] (* Harvey P. Dale, Aug 16 2015 *)

PROG

(PARI) for(n=1, 25, print1((7^n -3*5^n +3*4^n -4*3^n +3*2^n +2)/6, ", ")) \\ G. C. Greubel, Oct 07 2017

(MAGMA) [(7^n -3*5^n +3*4^n -4*3^n +3*2^n +2)/6: n in [1..25]]; // G. C. Greubel, Oct 07 2017

CROSSREFS

Cf. A051180.

Sequence in context: A176023 A067220 A057684 * A167254 A140455 A041314

Adjacent sequences:  A053150 A053151 A053152 * A053154 A053155 A053156

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Goran Kilibarda, Feb 28 2000

EXTENSIONS

More terms from James A. Sellers, Mar 01 2000

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 August 23 22:20 EDT 2019. Contains 326254 sequences. (Running on oeis4.)