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A073591 A000522(n)+1. 4

%I

%S 2,3,6,17,66,327,1958,13701,109602,986411,9864102,108505113,

%T 1302061346,16926797487,236975164806,3554627472077,56874039553218,

%U 966858672404691,17403456103284422,330665665962404001,6613313319248080002

%N A000522(n)+1.

%C a(n) is an upper bound on the Ramsey numbers in A003323. - D. G. Rogers, Aug 27 2006

%C There is a nice derivation of the recurrence relation given in the Walker reference.

%H Vincenzo Librandi and Alois P. Heinz, <a href="/A073591/b073591.txt">Table of n, a(n) for n = 0..200</a> (28 terms from Vincenzo Librandi)

%H R. C. Walker, <a href="http://www.jstor.org/stable/3615645">A graph coloring theorem</a>, Math. Gaz., 60 (1976), 54-57.

%F Conjecture: a(n) +(-n-2)*a(n-1) +(2*n-1)*a(n-2) +(-n+2)*a(n-3)=0. - _R. J. Mathar_, Feb 16 2014

%p a:= proc(n) a(n):= `if`(n=0, 2, n*a(n-1)-n+2) end:

%p seq(a(n), n=0..30); # _Alois P. Heinz_, Feb 17 2014

%t f[n_] := n*(f[n - 1] - 1) + 2;f[0]=2; ff[n_]:=(1/(1+n))(1+E*Gamma[1+n, 1]-E*(n^2)*Gamma[1+n, 1]+E*n*Gamma[2+n, 1]) (Spindler)

%t Table[FunctionExpand[Gamma[n, 1] E] + 1, {n, 2, 29}] (* _Vincenzo Librandi_, Feb 17 2014 *)

%Y Cf. A003323, A001339.

%K nonn

%O 0,1

%A _Vladeta Jovovic_, Aug 28 2002

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Last modified March 8 00:38 EST 2021. Contains 341934 sequences. (Running on oeis4.)