OFFSET
1,1
FORMULA
a(n) = A000668(n) + 2 (conjectured). - Michel Marcus, Mar 21 2014
EXAMPLE
First perfect number is 6, its two prime factors are 2 and 3, so a(1) = 5.
MATHEMATICA
(* based on the code of Harvey P. Dale in A000396 *)
perf=(# (#+1))/2&/@Select[2^Range[1000]-1, PrimeQ];
spf[n_]:=Total[First/@FactorInteger[n]]; spf/@perf (* Ivan N. Ianakiev, Jul 11 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Madaline McCluskey, Mar 21 2014
EXTENSIONS
Typo in data corrected by Michel Marcus, Mar 21 2014
STATUS
approved