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A138113 Smallest number with same number of divisors as n*a(n-1). 3
1, 2, 6, 24, 120, 720, 5040, 27720, 166320, 1441440, 7207200, 73513440, 367567200, 4655851200, 64250746560, 1028011944960, 5140059724800, 32607253879200, 260858031033600, 4620913692595200, 97039187544499200, 897612484786617600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..22.

FORMULA

a(n) = A140635(n*a(n-1)) - J. Lowell, May 20 2008

EXAMPLE

5040*8=40320 has 96 divisors, but smallest number with 96 divisors is 27720

PROG

(PARI) A138113(n)={ local(an1, t) ; if(n<=2, return(n) ) ; an1 = A138113(n-1) ; t=length(divisors(n*an1)) ; return(A005179(t)) ; } {for (n=1, 40, print1(A138113(n)", ") ; ) } [From R. J. Mathar, Mar 20 2010]

CROSSREFS

Cf. A019505 (2*a(n-1)).

Cf. A140635.

Sequence in context: A248769 A276841 A273694 * A045977 A177278 A173847

Adjacent sequences:  A138110 A138111 A138112 * A138114 A138115 A138116

KEYWORD

nonn

AUTHOR

J. Lowell, May 04 2008

EXTENSIONS

More terms from R. J. Mathar, Mar 20 2010

STATUS

approved

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Last modified January 23 01:55 EST 2018. Contains 298093 sequences.