login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A274535 a(n) = 5*sigma(n). 14
5, 15, 20, 35, 30, 60, 40, 75, 65, 90, 60, 140, 70, 120, 120, 155, 90, 195, 100, 210, 160, 180, 120, 300, 155, 210, 200, 280, 150, 360, 160, 315, 240, 270, 240, 455, 190, 300, 280, 450, 210, 480, 220, 420, 390, 360, 240, 620, 285, 465, 360, 490, 270, 600, 360, 600, 400, 450, 300, 840, 310, 480, 520, 635 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

5 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) in which the structure of every 72-degree-three-dimensional sector arises after the 72-degree-zig-zag folding of every row of the diagram of the isosceles triangle A237593. The top of the pyramid is a five-pointed star formed by five rhombuses (see Links section).

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

Omar E. Pol, Diagram of the triangle before the 72-degree-zig-zag folding (rows: 1..28)

Index entries for sequences related to sigma(n)

FORMULA

a(n) = 5*A000203(n) = A000203(n) + A239050(n) = A074400(n) + A272027(n).

Dirichlet g.f.: 5*zeta(s-1)*zeta(s). - Ilya Gutkovskiy, Jul 04 2016

MAPLE

with(numtheory): seq(5*sigma(n), n=1..64);

MATHEMATICA

Table[5 DivisorSigma[1, n], {n, 64}] (* Michael De Vlieger, Jul 04 2016 *)

PROG

(PARI) a(n) = 5 * sigma(n);

CROSSREFS

k times sigma(n), k=1..6: A000203, A074400, A272027, A239050, this sequence, A274536.

Cf. A237593.

Sequence in context: A045176 A273908 A271576 * A027184 A328249 A110702

Adjacent sequences:  A274532 A274533 A274534 * A274536 A274537 A274538

KEYWORD

nonn,easy

AUTHOR

Omar E. Pol, Jun 29 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 3 10:45 EST 2021. Contains 341762 sequences. (Running on oeis4.)