OFFSET
1,1
COMMENTS
Analogous to phibonacci numbers (A065557) and other sequences (see crossrefs).
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..70 (terms < 4*10^12)
EXAMPLE
psi(210) = 576 = 240 + 336 = psi(209) + psi(208), therefore 210 is in the sequence.
MATHEMATICA
psi[n_]:=If[n < 1, 0, n Sum[ MoebiusMu[ d]^2 / d, {d, Divisors @ n}]];
Select[Range[10^6], psi[#]==psi[#-1]+psi[#-2] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Aug 19 2017
EXTENSIONS
a(21)-a(26) from Giovanni Resta, Aug 26 2018
STATUS
approved