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A266000
Numbers n such that the symmetric representation of sigma(n) has at least two parts of distinct size.
1
9, 21, 25, 27, 33, 35, 39, 45, 49, 50, 51, 55, 57, 63, 65, 69, 70, 75, 77, 81, 85, 87, 91, 93, 95, 98, 99, 105, 110, 111, 115, 117, 119, 121, 123, 125
OFFSET
1,1
COMMENTS
In other words: numbers n such that the symmetric representation of sigma(n) has at least two parts with distinct number of cells.
For more information about the symmetric representation of sigma see A237270 and A237593.
EXAMPLE
The symmetric representation of sigma(9) = 13 in the first quadrant looks like this:
y
.
._ _ _ _ _ 5
|_ _ _ _ _|
. |_ _ 3
. |_ |
. |_|_ _ 5
. | |
. | |
. | |
. | |
. . . . . . . . |_| . . x
.
There are three parts: 5 + 3 + 5 = 13, so 9 is in the sequence because the structure contains at least two parts of distinct size.
KEYWORD
nonn,more
AUTHOR
Omar E. Pol, Dec 19 2015
STATUS
approved