A326122 a(n) = 10 * sigma(n).

10, 30, 40, 70, 60, 120, 80, 150, 130, 180, 120, 280, 140, 240, 240, 310, 180, 390, 200, 420, 320, 360, 240, 600, 310, 420, 400, 560, 300, 720, 320, 630, 480, 540, 480, 910, 380, 600, 560, 900, 420, 960, 440, 840, 780, 720, 480, 1240, 570, 930, 720, 980, 540, 1200, 720, 1200, 800, 900, 600, 1680, 620, 960

Offset: 1

Author

Omar E. Pol, Jul 13 2019

Keywords

• nonn
• easy

Comments

10 times the sum of the divisors of n.

a(n) is also the total number of horizontal rhombuses in the terraces of the n-th level of an irregular stepped pyramid (starting from the top) where the structure of every 36-degree-three-dimensional sector arises after the 36-degree-zig-zag folding of every row of the diagram of the isosceles triangle A237593. The top of the pyramid is a 10-pointed star formed by 10 rhombuses (see Links section).

Links

• Omar E. Pol, Diagram of the triangle A237593 before the 36-degree-zig-zag folding (rows: 1..28)
• Index entries for sequences related to sigma(n)

Crossrefs

k times sigma(n), k=1..9: A000203, A074400, A272027, A239050, A274535, A274536, A319527, A319528, A325299.

Cf. A008592, A033583, A124080, A124252, A142342, A153780, A237593.

Programs

GAP

List([1..70],n->10*Sigma(n)); # After Muniru A Asiru

Magma

[10*DivisorSigma(1, n): n in [1..70]]; // Vincenzo Librandi, Jul 26 2019

Maple

with(numtheory): seq(10*sigma(n), n=1..64);

Mathematica

10*DivisorSigma[1,Range[70]] (* After Harvey P. Dale *)

PARI

a(n) = 10 * sigma(n);

Formula

a(n) = 10*A000203(n) = 5*A074400(n) = 2*A274535(n).

a(n) = A000203(n) + A325299(n) = A074400(n) + A319528(n).

Dirichlet g.f.: 10*zeta(s-1)*zeta(s). - (After Ilya Gutkovskiy)