# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a055484 Showing 1-1 of 1 %I A055484 #19 Jun 10 2024 16:42:52 %S A055484 1,4,14,39,96,213,437,837,1520,2632,4380,7040,10979,16668,24716,35879, %T A055484 51104,71549,98625,134025,179782,238292,312386,405368,521083,663968, %U A055484 839140,1052439,1310534,1620985,1992343,2434229,2957458,3574108 %N A055484 Number of unlabeled 3-element intersecting families (with not necessarily distinct sets) of an n-element set. %H A055484 G. C. Greubel, Table of n, a(n) for n = 1..1000 %H A055484 V. Jovovic, G. Kilibarda, On the number of Boolean functions in the Post classes F^{mu}_8, (in Russian), Diskretnaya Matematika, 11 (1999), no. 4, 127-138. %H A055484 V. Jovovic, G. Kilibarda, On the number of Boolean functions in the Post classes F^{mu}_8, (English translation), Discrete Mathematics and Applications, 9, (1999), no. 6. %H A055484 Index entries for linear recurrences with constant coefficients, signature (4, -4, -2, 2, 4, 3, -12, 3, 4, 2, -2, -4, 4, -1). %F A055484 G.f.: -x*(x^3-x^2-1)*(x^6+x^4+2*x^3+x^2+1)/((x^3-1)^2*(x^2-1)^2*(x-1)^4). %t A055484 Rest[CoefficientList[Series[-x*(x^3 - x^2 - 1)*(x^6 + x^4 + 2*x^3 + x^2 + 1)/((x^3 - 1)^2*(x^2 - 1)^2*(x - 1)^4), {x, 0, 50}], x]] (* _G. C. Greubel_, Oct 06 2017 *) %t A055484 LinearRecurrence[{4,-4,-2,2,4,3,-12,3,4,2,-2,-4,4,-1},{1,4,14,39,96,213,437,837,1520,2632,4380,7040,10979,16668},40] (* _Harvey P. Dale_, Jun 10 2024 *) %o A055484 (PARI) x='x+O('x^50); Vec(-x*(x^3-x^2-1)*(x^6+x^4+2*x^3+x^2+1)/( (x^3-1)^2*(x^2-1)^2*(x-1)^4)) \\ _G. C. Greubel_, Oct 06 2017 %Y A055484 Cf. A053155 (labeled case), A005783, A002727, A051180. %K A055484 nonn %O A055484 1,2 %A A055484 _Vladeta Jovovic_, Goran Kilibarda, Jul 03 2000 %E A055484 More terms from _James A. Sellers_, Jul 04 2000 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE