A262619 Number of parts in the symmetric representation of sigma(n) in two successive octants of two quadrants.

1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 3, 3, 3, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 5, 1, 3, 1, 1, 1, 3, 3, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 5, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 1, 3, 1, 3, 1, 1, 3, 5, 1, 1, 1, 1, 1, 3, 1

Offset

1,9

Comments

In the diagram of the top view of the pyramid described in A244050 consider a 90-degree sector on two successive octants of two quadrants. The area of the top triangle is equal to 1 and the sum of the areas of all parts (or regions) added at n-th stage equals sigma(n), the sum of the divisors of n.

a(n) is also the number of terraces at n-th level (starting from the top) in the mentioned sector of the pyramid.

For more information see A237593 and A237270.

Links

Antti Karttunen, Table of n, a(n) for n = 1..5000 (computed from the b-file of A237271 provided by Michel Marcus)

Formula

a(n) = A237271(n), if A237271(n) is odd.

a(n) = A237271(n) - 1, if A237271(n) is even.

Crossrefs

Cf. A000203, A196020, A235791, A236104, A237270, A237271, A237591, A237593, A244050, A244971, A245092, A262618.

Sequence in context: A130046 A349509 A378645 * A166123 A272334 A014491

Adjacent sequences: A262616 A262617 A262618 * A262620 A262621 A262622

Keyword

nonn

Author

Omar E. Pol, Nov 06 2015

Status

approved