

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
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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



