OFFSET
1,2
COMMENTS
Paraphrasing Doug Iannucci, n is called a "leap year number" if tau(phi(n)) = phi(tau(n))^2 (366 is a leap year number, hence the sequence name). The beast number is a leap year number. The only prime leap year number is 2.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
phi(666)=216, tau(216)=16, tau(666)=12, phi(12)=4, 4^2=16, therefore 666 is in the sequence.
MATHEMATICA
Select[Range[1000], DivisorSigma[0, EulerPhi[#]] == EulerPhi[DivisorSigma[0, #]]^2 &]
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jean-François Alcover, Jun 24 2013
STATUS
approved