1,2

Achim Flammenkamp, The Multiply Perfect Numbers Page,

a(4)=4 because the smallest 4-perfect number factorization is 2^5*3^3*5*7, which has 4 different prime factors.

Sequence in context: A080023 A080074 A018064 this_sequence A058521 A116628 A140463

Adjacent sequences: A107478 A107479 A107480 this_sequence A107482 A107483 A107484

hard,more,nonn

Jose Brox (tautocrona(AT)terra.es), May 27 2005