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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A097464 5-infinitary perfect numbers: n such that 5-infinitary-sigma(n)=2*n. 1
6, 28, 496, 47520, 288288, 308474880 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Here 5-infinitary-sigma(a) means sum of 5-infinitary-divisor of a. If n=Product p_i^r_i and d=Product p_i^s_i, each s_i has a digit a<=b in its 5-ary expansion everywhere that the corresponding r_i has a digit b, then d is a 5-infinitary-divisor of n.

Is it certain that 308474880 is the 6th term? M. F. Hasler, Nov 20 2010

LINKS

Table of n, a(n) for n=1..6.

FORMULA

{n: A097863(n) = 2*n}.

EXAMPLE

Factorizations: 2*3, 2^2*7, 2^4*31, 2^5*3^3*5*11, 2^5*3^2*7*11*13, 2^10*3*5*7*19*151

CROSSREFS

Cf. A074849.

Sequence in context: A000396 A152953 A066239 * A166998 A038182 A095723

Adjacent sequences:  A097461 A097462 A097463 * A097465 A097466 A097467

KEYWORD

nonn

AUTHOR

Yasutoshi Kohmoto

EXTENSIONS

Missing a(4) inserted by R. J. Mathar, Nov 20 2010

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified February 23 23:30 EST 2018. Contains 299595 sequences. (Running on oeis4.)