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 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

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