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 A066240 The floor(n/2)-perfect numbers, where f-perfect numbers for an arithmetical function f are defined in A066218. 0
 18, 20, 70, 104, 464, 1952 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS J. Pe, On a Generalization of Perfect Numbers, J. Rec. Math., 31(3) (2002-2003), 168-172. EXAMPLE 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. MATHEMATICA f[x_] := Floor[x/2]; Select[ Range[ 1, 10^5], 2 * f[ # ] == Apply[ Plus, Map[ f, Divisors[ # ] ] ] & ] CROSSREFS Sequence in context: A075865 A250113 A182226 * A115747 A303686 A185099 Adjacent sequences:  A066237 A066238 A066239 * A066241 A066242 A066243 KEYWORD nonn AUTHOR Joseph L. Pe, Dec 19 2001 STATUS approved

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Last modified January 17 18:48 EST 2019. Contains 319251 sequences. (Running on oeis4.)