login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A057449 Product of differences between consecutive positive divisors of n. 2
1, 1, 2, 2, 4, 3, 6, 8, 12, 15, 10, 12, 12, 35, 40, 64, 16, 81, 18, 100, 112, 99, 22, 192, 80, 143, 216, 588, 28, 600, 30, 1024, 352, 255, 224, 1944, 36, 323, 520, 2400, 40, 3087, 42, 3388, 2880, 483, 46, 12288, 252, 5625, 952, 6084, 52, 19683, 1056, 14112, 1216 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row products of triangle A193829, if n >= 2. - Omar E. Pol, Aug 31 2011

When p is prime a(p) = p-1. - Michel Marcus, May 15 2014

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = product(A027750(n,k+1)-A027750(n,k): k=1..A001221(n)-1. - Reinhard Zumkeller, Jun 23 2013

EXAMPLE

Since positive divisors of 12 are 1, 2, 3, 4, 6 and 12, a(12) = (2-1) *(3-2) *(4-3) *(6-4) *(12-6) = 1 *1 *1 *2 *6 = 12.

MATHEMATICA

Times@@Differences[Divisors[#]]&/@Range[80]  (* Harvey P. Dale, Apr 20 2011 *)

PROG

(Haskell)

a057449 = product . a193829_row  -- Reinhard Zumkeller, Jun 23 2013

(PARI) a(n) = {my(d = divisors(n)); prod(i=1, #d-1, d[i+1] - d[i]); } \\ Michel Marcus, May 15 2014

CROSSREFS

Sequence in context: A293170 A101200 A122585 * A286931 A265701 A007439

Adjacent sequences:  A057446 A057447 A057448 * A057450 A057451 A057452

KEYWORD

nonn,look

AUTHOR

Leroy Quet, Sep 25 2000

STATUS

approved

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 11 04:29 EST 2018. Contains 318049 sequences. (Running on oeis4.)