A266094 a(n) is the sum of the divisors of the smallest number k such that the symmetric representation of sigma(k) has n parts.

1, 4, 13, 32, 104, 228, 576, 1408, 4104, 9824, 19152, 39816, 82944, 196992, 441294, 881280, 1911168, 4539024

Offset

1,2

Comments

For more information see A239663 and A239665.

Links

Table of n, a(n) for n=1..18.

Formula

a(n) = A000203(A239663(n)).

Example

Illustration of the symmetric representation of sigma(9):
.
.     _ _ _ _ _ 5
.    |_ _ _ _ _|
.              |_ _ 3
.              |_  |
.                |_|_ _ 5
.                    | |
.                    | |
.                    | |
.                    | |
.                    |_|
.
For n = 3 we have that 9 is the smallest number whose symmetric representation of sigma has three parts: [5, 3, 5], so a(3) = 5 + 3 + 5 = 13, equaling the sum of divisors of 9: sigma(9) = 1 + 3 + 9 = 13.
For n = 7 we have that 357 is the smallest number whose symmetric representation of sigma has seven parts: [179, 61, 29, 38, 29, 61, 179], so a(7) = 179 + 61 + 29 + 38 + 29 + 61 + 179 = 576, equaling the sum of divisors of 357: sigma(357) = 1 + 3 + 7 + 17 + 21 + 51 + 119 + 357 = 576.

Crossrefs

Cf. A000203, A196020, A235791, A236104, A237048, A237270, A237271, A237591, A237593, A239931-A239934, A239663, A239665, A240062, A245092, A262626.

Sequence in context: A208638 A173277 A036420 * A054039 A302082 A124669

Adjacent sequences: A266091 A266092 A266093 * A266095 A266096 A266097

Keyword

nonn,hard,more

Author

Omar E. Pol, Dec 21 2015

Extensions

a(14)-a(18) from Omar E. Pol, Jul 21 2018

Status

approved