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 A078545 Largest prime dividing tau(n), the number of divisors of n. 1
 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 5, 2, 3, 2, 3, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 2, 5, 3, 3, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 3, 7, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 3, 3, 2, 2, 2, 5, 5, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 3, 2, 3, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS From Robert Israel, Dec 04 2016: (Start) a(n)=2 if and only if every member of the prime signature of n is of the form 2^k-1. a(m*k) = max(a(m),a(k)) if m and k are coprime. (End) LINKS Robert Israel, Table of n, a(n) for n = 2..10000 FORMULA a(n) = A006530(A000005(n)). MAPLE f:= n -> max(numtheory:-factorset(numtheory:-tau(n))): map(f, [\$2..100]); # Robert Israel, Dec 04 2016 PROG (PARI) a(n) = vecmax(factor(numdiv(n))[, 1]); \\ Michel Marcus, Dec 05 2016 CROSSREFS Cf. A000005, A006530, A078542, A078543, A078544, A124010. Sequence in context: A329614 A134852 A071188 * A163105 A152235 A278966 Adjacent sequences:  A078542 A078543 A078544 * A078546 A078547 A078548 KEYWORD nonn AUTHOR Labos Elemer, Dec 05 2002 EXTENSIONS a(2)=2 inserted by Robert Israel, Dec 04 2016 STATUS approved

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Last modified September 23 02:41 EDT 2021. Contains 347609 sequences. (Running on oeis4.)