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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A064147 Numbers n such that n! - 1 and n! + 1 have the same number of divisors, i.e., tau(n! - 1) = tau(n! + 1). 1
3, 8, 10, 13, 17, 20, 22, 24, 26, 34, 39, 53, 59, 61, 63, 69, 70, 76, 80, 87, 97, 99, 103, 124, 130 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The list is complete to 102. 200 and 392 are also to be included.

236 and 634 are terms. - Chai Wah Wu, Jan 03 2020

LINKS

Table of n, a(n) for n=1..25.

Paul Leyland, Generalized Cullen and Woodall numbers

Andrew Walker, N!+/-1 Factoring Page

PROG

(PARI) {A064147(n)=if(numdiv(n!-1)==numdiv(n!+1), n, 0)}

CROSSREFS

Cf. A000005.

Sequence in context: A226641 A212966 A074186 * A287573 A122529 A137920

Adjacent sequences:  A064144 A064145 A064146 * A064148 A064149 A064150

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Sep 11 2001

EXTENSIONS

More terms from Randall L. Rathbun, Jan 11 2002

a(23)-a(25) from Chai Wah Wu, Jan 03 2020

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 July 24 06:56 EDT 2021. Contains 346273 sequences. (Running on oeis4.)