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Colum Column h gives the n-th second hexagonal number (A014105).
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The characteristic shape of the symmetric representation of a(n) consists in that in the main diagonal of the diagram the smallest Dyck path has a pick peak and the largest Dyck path has a valley.
On the other hand we can see that in the main diagonal of every diagram the smallest Dyck path has a pick peak and the largest Dyck path has a valley as shown below.
Some sequences that gives sum of divisors: A000225 (of powers of 2), A008864 (of prime numbers), A065764 (of squares), A073255 (of composites), A074285 (of triangular numbers, also of generalized hexagonal numbers), A139256 (of perfect numbers), A175926 (of cubes), A224613 (of multiples of 6), A346865 (of hexagonal numbers), A346867 (of numbers with middle divisors), A346868 (of numbers with no middle divisors), A347155 (of nontriangular numbers).
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