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!)
A261030 Numbers k such that sqrt(k + sqrt(k + sqrt(k + ...))) is an even perfect number. 0
30, 756, 245520, 66056256, 1125625012162560, 73785850390636462080, 18889393873815823712256, 5316911978187903333320785637991776256 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..8.

Eric Weisstein's World of Mathematics, PerfectNumber

FORMULA

a(n) = 2^(A000043(n) - 2)*(2^A000043(n) - 2)*(2^A000043(n) - 1)*(2^A000043(n) + 1).

EXAMPLE

For n = 1, a(1) = 30 since sqrt(30 + sqrt(30 + sqrt(30 + ...))) = 6, which is an even perfect number.

CROSSREFS

Cf. A000396, A000043.

Sequence in context: A089507 A045689 A096722 * A176646 A160269 A049394

Adjacent sequences:  A261027 A261028 A261029 * A261031 A261032 A261033

KEYWORD

nonn

AUTHOR

Ilya Gutkovskiy, Aug 07 2015

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 12 10:20 EDT 2020. Contains 335657 sequences. (Running on oeis4.)