%I A087811
%S A087811 1,2,4,6,9,12,16,20,25,30,36,42,49,56,64,72,81,90,100,110,121,132,144,
%T A087811 156,169,182,196,210,225,240,256,272,289,306,324,342,361,380,400,420,
%U A087811 441,462,484,506,529,552,576,600,625,650,676,702,729,756,784,812,841
%N A087811 Numbers n such that ceil(sqrt(n)) divides n.
%C A087811 Essentially the same as the quarter-squares A002620.
%C A087811 Nonsquare elements of this sequence are given by A002378. - Max Alekseyev 
               (maxale(AT)gmail.com), Nov 27 2006
%F A087811 a(n) = (n + n mod 2)*(n + 2 - n mod 2)/4.
%F A087811 Numbers of the form k^2 or k^2 - k. - Don Reble, Oct 17, 2003
%F A087811 a(1) = 1, a(2) = 2, a(n) = n + a(n - 2) - Alonso Delarte (alonso.delarte(AT)gmail.com), 
               Jun 18 2005
%t A087811 a[1] := 1; a[2] := 2; a[n_] := n + a[n - 2]; Table[a[n], {n, 57}] (Delarte)
%Y A087811 Cf. A006446, A003059, A002620.
%Y A087811 Cf. A002378, A006446.
%Y A087811 Sequence in context: A083392 A076921 A002620 this_sequence A025699 A024617 
               A025698
%Y A087811 Adjacent sequences: A087808 A087809 A087810 this_sequence A087812 A087813 
               A087814
%K A087811 nonn
%O A087811 1,2
%A A087811 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 16 2003