The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A122180 Number of ways to write n as n = x*y*z with 1 < x < y < z < n. 9
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 3, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 3, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0, 3, 0, 0, 0, 1, 0, 3, 0, 0, 0, 0, 0, 4, 0, 0, 0, 1, 0, 1, 0, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,48 COMMENTS x,y,z are distinct proper factors of n. See A122181 for n such that a(n) > 0. LINKS Antti Karttunen, Table of n, a(n) for n = 1..1001 FORMULA a(n) = A200214(n)/6. - Antti Karttunen, Jul 08 2017 EXAMPLE a(48) = 2 because 48 = 2*3*8 = 2*4*6, two products of three distinct proper factors of 48. PROG (PARI) for(n=1, 105, t=0; for(x=2, n-1, for(y=x+1, n-1, for(z=y+1, n-1, if(x*y*z==n, t++)))); print1(t, ", ")) (PARI) A122180(n) = { my(s=0); fordiv(n, x, if((x>1)&&(x

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 13 08:10 EDT 2021. Contains 344981 sequences. (Running on oeis4.)