1,2

Note that 1 is regarded as free of prime squares and also a square number and it is also a unitary divisor.

S. R. Finch, Unitarism and infinitarism.

Multiplicative with a(p)=2 and a(p^e)=1 for e>1. a(n)=2^A056169(n). - Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 01 2001

n=252=2.2.3.3.7 has 18 divisors, 8 unitary and 8 square-free divisors of which 2 are unitary and square-free,divisors {1,7}; n=2520=2.2.2.3.3.5.7 has 48 divisors,16 unitary and 16 square-free divisors of which {1,5,7,35}, i.e. a(2520)=4

a(2520)=a(2^3*3^2*5*7)=a(2^3)*a(3^2)*a(5)*a(7)=1*1*2*2=4.

a(n) = A000005[A055231(n)] = A000005[A007913(n)/A055229(n)]

Sequence in context: A007427 A048106 A156260 this_sequence A055076 A069780 A066954

Adjacent sequences: A056668 A056669 A056670 this_sequence A056672 A056673 A056674

mult,nonn

Labos E. (labos(AT)ana.sote.hu), Aug 10 2000