|
%I #12 Sep 26 2019 09:05:37
%S 18,20,70,104,464,1952,45356,91388,130304,254012,388076,437745,522752,
%T 8382464,134193152
%N The floor(n/2)-perfect numbers, where f-perfect numbers for an arithmetical function f are defined in A066218.
%H 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 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 f[x_] := Floor[x/2]; Select[ Range[ 1, 10^5], 2 * f[ # ] == Apply[ Plus, Map[ f, Divisors[ # ] ] ] & ]
%Y Cf. A066218.
%K nonn,more
%O 1,1
%A _Joseph L. Pe_, Dec 19 2001
%E a(7)-a(15) from _Amiram Eldar_, Sep 26 2019
|
