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 A095154 Number of 5-block covers of a labeled n-set. 1
 21, 2919, 155106, 6054006, 208493607, 6791135085, 215553311652, 6758354401932, 210657488261913, 6547648042583571, 203236346721890118, 6304217491485837378, 195489116558570607339, 6061038320388658194777, 187905324183802270088904, 5825262097993829801550744 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS Index entries for linear recurrences with constant coefficients, signature (57,-1002,6562,-15381,9765). FORMULA a(n) = (1/5!)*(274-225*3^n+85*7^n-15*15^n+31^n). G.f.: -21*x^3*(465*x^2+82*x+1) / ((x-1)*(3*x-1)*(7*x-1)*(15*x-1)*(31*x-1)). - Colin Barker, Jul 13 2013 a(n) = sum(i=0..n, (-1)^i * C(n,i) * C(2^(n-i)-1,5) ). - Geoffrey Critzer, Aug 24 2014 a(n) = 57*a(n-1)-1002*a(n-2)+6562*a(n-3)-15381*a(n-4)+9765*a(n-5). - Wesley Ivan Hurt, Aug 25 2014 MAPLE A095154:=n->(274-225*3^n+85*7^n-15*15^n+31^n)/120: seq(A095154(n), n=3..20); # Wesley Ivan Hurt, Aug 25 2014 MATHEMATICA nn = 19; Table[Sum[(-1)^i Binomial[n, i] Binomial[2^(n - i) - 1, 5], {i, 0, n}], {n, 3, nn}] (* Geoffrey Critzer, Aug 24 2014 *) Table[(274 - 225*3^n + 85*7^n - 15*15^n + 31^n)/120, {n, 3, 20}] (* Wesley Ivan Hurt, Aug 25 2014 *) PROG (Magma) [(274-225*3^n+85*7^n-15*15^n+31^n)/120 : n in [3..20]]; // Wesley Ivan Hurt, Aug 25 2014 CROSSREFS Column of A055154. Sequence in context: A114934 A098375 A202793 * A220999 A231825 A347604 Adjacent sequences: A095151 A095152 A095153 * A095155 A095156 A095157 KEYWORD easy,nonn AUTHOR Vladeta Jovovic, May 31 2004 EXTENSIONS More terms from Colin Barker, Jul 13 2013 STATUS approved

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Last modified March 21 10:30 EDT 2023. Contains 361402 sequences. (Running on oeis4.)