OFFSET
1,3
COMMENTS
Row n of table represents second signature of A025487(n) (cf. A212172). The use of 0 in the table to represent numbers with no exponents >=2 in their prime factorization accords with the usual OEIS practice of using 0 to represent nonexistent elements when possible. In comments, the second signature of squarefree numbers is represented as { }.
LINKS
Will Nicholes, Prime Signatures
EXAMPLE
240 = 2^4*3*5 has 1 exponent in its canonical prime factorization that equals or exceeds 2 (namely, 4). Hence, 240's second signature is {4}. Since 240 = A025487(24), row 24 of the table represents the second signature {4}.
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Matthew Vandermast, Jun 03 2012
STATUS
approved