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 A053157 Number of 3-element intersecting families (with not necessary distinct sets) whose union is an n-element set. 1
 1, 5, 32, 235, 1816, 14055, 107052, 800315, 5886416, 42739855, 307295572, 2193374595, 15571898616, 110121224855, 776543100092, 5464689616075, 38398915520416, 269529406433055, 1890416947176612, 13251578251332755 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 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 Index to sequences with 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+2*3^n-3*2^n+2). G.f.: -x*(280*x^5-475*x^4+339*x^3-112*x^2+17*x-1)/((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)*(7*x-1)). [Colin Barker, Jul 29 2012] CROSSREFS Cf. A051180. Sequence in context: A065071 A153396 A146965 * A102231 A127089 A208046 Adjacent sequences:  A053154 A053155 A053156 * A053158 A053159 A053160 KEYWORD easy,nonn AUTHOR Vladeta Jovovic, Goran Kilibarda (vladeta(AT)eunet.rs), Feb 28 2000 STATUS approved

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