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A275250 Odd numbers n that divide the number of divisors of n!. 1
1, 27, 45, 105, 125, 135, 175, 189, 225, 231, 243, 297, 315, 351, 375, 385, 405, 441, 455, 495, 525, 539, 567, 585, 595, 605, 625, 637, 663, 675, 693, 715, 729, 735, 741, 765, 819, 825, 845, 847, 855, 875, 891, 935, 945, 969, 975, 1001, 1029, 1035, 1045, 1053, 1089 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Odd terms of A051178.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

The odd number 27 is a term because A000005(27!) = 2^9*3^3*7^2 is divisible by 27.

MAPLE

N:= 2000: # to get all terms <= N

P:= select(isprime, [2, seq(i, i=3..N, 2)]):

d:= Vector(nops(P), 1):

A:= 1:

for n from 2 to N do

  f:= ifactors(n)[2];

  for t in f do

    if member(t[1], P, 'k') then

        d[k]:= d[k] + t[2]

    fi

  od:

  if n::odd and convert(d, `*`) mod n = 0 then A:= A, n fi;

od:

A; # Robert Israel, Aug 05 2016

MATHEMATICA

A275250Q = OddQ[#] && Divisible[DivisorSigma[0, #!], #] &; Select[Range[500], A275250Q] (* JungHwan Min, Jul 29 2016 *)

PROG

(PARI) isok(n) = (n % 2) && !(numdiv(n!) % n); \\ Michel Marcus, Jul 26 2016

CROSSREFS

Cf. A051178, A027423.

Sequence in context: A039325 A043148 A043928 * A223019 A059658 A241407

Adjacent sequences:  A275247 A275248 A275249 * A275251 A275252 A275253

KEYWORD

nonn

AUTHOR

Altug Alkan, Jul 21 2016

STATUS

approved

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Last modified April 18 08:37 EDT 2019. Contains 322209 sequences. (Running on oeis4.)