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A030232
Numbers k such that the number of divisors of k! divides the number of divisors of (2k)!.
1
1, 2, 4, 8, 10, 13, 20, 22, 24, 32, 33, 34, 37, 42, 56, 68, 75, 100, 102, 108, 114, 129, 133, 134, 136, 148, 149, 153, 159, 161, 162, 186, 187, 248, 249, 254, 277, 300, 301, 310, 311, 330, 331, 351, 380, 381, 382, 388, 411, 423, 430, 488, 489, 531, 545, 556
OFFSET
1,2
COMMENTS
Numbers k such that A000005(k!) divides A000005((2k)!).
LINKS
MATHEMATICA
Select[Range[560], Divisible[DivisorSigma[0, (2#)!], DivisorSigma[ 0, #!]]&] (* Harvey P. Dale, Mar 06 2015 *)
PROG
(PARI) isok(n) = (numdiv((2*n)!) % numdiv(n!)) == 0; \\ Michel Marcus, Apr 16 2015
CROSSREFS
Cf. A000005 (number of divisors), A027423 (number of divisors of n!).
Sequence in context: A141400 A190744 A190751 * A102024 A104197 A323440
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Sep 28 2002
STATUS
approved