A336616 Maximum divisor of n! with distinct prime multiplicities.

1, 1, 2, 3, 24, 40, 720, 1008, 8064, 72576, 3628800, 5702400, 68428800, 80870400, 317011968, 118879488000, 1902071808000, 2487324672000, 44771844096000, 50039119872000, 1000782397440000, 21016430346240000, 5085976143790080000, 6156707963535360000

Offset

0,3

Comments

A number's prime signature (row n of A124010) is the sequence of positive exponents in its prime factorization, so a number has distinct prime multiplicities iff all the exponents in its prime signature are distinct.

Links

David A. Corneth, Table of n, a(n) for n = 0..589

Gus Wiseman, Sequences counting and encoding certain classes of multisets

Formula

a(n) = A327498(n!).

Example

The sequence of terms together with their prime signatures begins:
             1: ()
             1: ()
             2: (1)
             3: (1)
            24: (3,1)
            40: (3,1)
           720: (4,2,1)
          1008: (4,2,1)
          8064: (7,2,1)
         72576: (7,4,1)
       3628800: (8,4,2,1)
       5702400: (8,4,2,1)
      68428800: (10,5,2,1)
      80870400: (10,5,2,1)
     317011968: (11,5,2,1)
  118879488000: (11,6,3,2,1)

Mathematica

Table[Max@@Select[Divisors[n!], UnsameQ@@Last/@If[#==1, {}, FactorInteger[#]]&], {n, 0, 15}]

Prog

(PARI) a(n) = { if(n < 2, return(1)); my(pr = primes(primepi(n)), res = pr[#pr]); for(i = 1, #pr, pr[i] = [pr[i], val(n, pr[i])] ); forstep(i = #pr, 2, -1, if(pr[i][2] < pr[i-1][2], res*=pr[i-1][1]^pr[i-1][2] ) ); res }
val(n, p) = my(r=0); while(n, r+=n\=p); r \\ David A. Corneth, Aug 25 2020

Crossrefs

A327498 is the version not restricted to factorials, with quotient A327499.

A336414 counts these divisors.

A336617 is the quotient n!/a(n).

A336618 is the version for equal prime multiplicities.

A130091 lists numbers with distinct prime multiplicities.

A181796 counts divisors with distinct prime multiplicities.

A327526 gives the maximum divisor of n with equal prime multiplicities.

A336415 counts divisors of n! with equal prime multiplicities.

Cf. A000005, A000110, A098859, A118914, A124010, A336424, A336500, A336568.

Factorial numbers: A000142, A007489, A022559, A027423, A048656, A048742, A071626, A325272, A325273, A325617, A336416.

Sequence in context: A092049 A257789 A377825 * A354278 A061778 A160667

Adjacent sequences: A336613 A336614 A336615 * A336617 A336618 A336619

Keyword

nonn

Author

Gus Wiseman, Jul 29 2020

Status

approved