OFFSET
1,1
COMMENTS
a(n) is also the number of toothpicks added at n-th stage in the toothpick structure of the symmetric representation of sigma in two quadrants (without the axis x and y).
FORMULA
EXAMPLE
Illustration of a(9) = 32:
. 12
. _ _ _ _ _
. |_ _ _ _ _|
. _ _ 8
. |_ |
. |_| _
. | |
. | |
. | | 12
. | |
. |_|
.
For n = 9 the symmetric representation of sigma(9) = 13 has three parts of areas 5, 3, 5 respectively. The perĂmeters of the parts are 12, 8 and 12 as shown above. The sum of the perimeters is 12 + 8 + 12 = 32, so a(9) = 32.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Omar E. Pol, Dec 11 2016
EXTENSIONS
a(29)-a(32) from Omar E. Pol, May 04 2023
STATUS
approved