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!)
A072862 The smallest k>1 such that k divides sigma(k*n) is equal to 6. 8
1, 4, 9, 16, 25, 36, 64, 81, 100, 121, 144, 225, 256, 289, 324, 400, 484, 529, 576, 625, 729, 841, 900, 1024, 1089, 1156, 1296, 1600, 1681, 1936, 2025, 2116, 2209, 2304, 2401, 2500, 2601, 2809, 2916, 3025, 3364, 3481, 3600, 4096, 4356, 4624, 4761, 5041 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The smallest k>1 such that k divides sigma(k*n) is always 2, 3 or 6. Sequence generates squares but not all the squares (49, 169, 196, 361, 441, 676, 784, ... are the first squares not in the sequence).

This is not the sequence of solutions to sigma(n) == 1 (mod 6), because 2401 is in this sequence but sigma(2401) == 5 (mod 6). See A074384 for more examples. - R. J. Mathar, May 19 2020

LINKS

Table of n, a(n) for n=1..48.

FORMULA

{n: A049605(n) = 6}. - R. J. Mathar, May 19 2020

CROSSREFS

Sequence in context: A309002 A328953 A328558 * A300303 A062295 A238203

Adjacent sequences:  A072859 A072860 A072861 * A072863 A072864 A072865

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Jul 26 2002

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 June 25 10:28 EDT 2021. Contains 345453 sequences. (Running on oeis4.)