%I A055503
%S A055503 1,1,2,7,18,41,85,162,287,478,756,1145,1672,2367,3263,4396,5805,
%T A055503 7532,9622,12123,15086,18565,22617,27302,32683,38826,45800,53677,
%U A055503 62532,72443,83491,95760,109337,124312,140778,158831,178570,200097
%N A055503 Take n points in general position in plane; draw all lines joining them; 
               sequence gives number of connected regions formed.
%D A055503 L. Comtet, Advanced Combinatorics, Reidel, 1974, Problem 1, p. 72; and 
               Problem 8, p. 74.
%H A055503 Author?, <a href="http://physolymp.fml31.ru/olymp/files/f194.pdf">Title?</
               a> (from Alexander Evnin (graph98(AT)yandex.ru), Dec 06 2008)
%F A055503 (1/8)*(n-1)*(n^3-5*n^2+18*n-8) for n>1.
%p A055503 A055503 := n->(1/8)*(n^4-6*n^3+23*n^2-26*n+8); [for n >1]
%Y A055503 Cf. A000124.
%Y A055503 Sequence in context: A086741 A051743 A054111 this_sequence A077802 A095151 
               A147611
%Y A055503 Adjacent sequences: A055500 A055501 A055502 this_sequence A055504 A055505 
               A055506
%K A055503 nonn,nice
%O A055503 0,3
%A A055503 N. J. A. Sloane (njas(AT)research.att.com), Jul 10 2000
%E A055503 a(1) changed from 0 to 1 by N. J. A. Sloane (njas(AT)research.att.com), 
               Dec 07 2008