This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A066240 #12 Sep 26 2019 09:05:37 %S A066240 18,20,70,104,464,1952,45356,91388,130304,254012,388076,437745,522752, %T A066240 8382464,134193152 %N A066240 The floor(n/2)-perfect numbers, where f-perfect numbers for an arithmetical function f are defined in A066218. %H A066240 J. Pe, <a href="http://jlpe.tripod.com/gpn/fperfect.htm">On a Generalization of Perfect Numbers</a>, J. Rec. Math., 31(3) (2002-2003), 168-172. %e A066240 Let f(n) = floor(n/2). Then f(18) = 9 = 4+3+1+1+0 = f(9)+f(6)+f(3)+f(2)+f(1); so 18 is a term of the sequence. %t A066240 f[x_] := Floor[x/2]; Select[ Range[ 1, 10^5], 2 * f[ # ] == Apply[ Plus, Map[ f, Divisors[ # ] ] ] & ] %Y A066240 Cf. A066218. %K A066240 nonn,more %O A066240 1,1 %A A066240 _Joseph L. Pe_, Dec 19 2001 %E A066240 a(7)-a(15) from _Amiram Eldar_, Sep 26 2019