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!)
A157020 a(n) = Sum_{d|n} d*binomial(n/d+d-2,d-1). 4
1, 3, 4, 9, 6, 22, 8, 33, 28, 46, 12, 131, 14, 78, 136, 177, 18, 307, 20, 456, 302, 166, 24, 1149, 376, 222, 568, 1177, 30, 2387, 32, 1761, 958, 358, 2556, 5224, 38, 438, 1496, 7851, 42, 8317, 44, 4863, 9136, 622, 48, 20169, 6518, 11451, 3112, 8516, 54, 23734 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Equals row sums of triangle A157497. [Gary W. Adamson & Mats Granvik, Mar 01 2009]

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..10000

FORMULA

G.f.: Sum_{n>=1} n*x^n/(1-x^n)^n.

MAPLE

add( d*binomial(n/d+d-2, d-1), d=numtheory[divisors](n) ) ;

PROG

(PARI) N=66; x='x+O('x^N); Vec(sum(k=1, N, k*x^k/(1-x^k)^k)) \\ Seiichi Manyama, Sep 03 2019

CROSSREFS

Cf. A081543, A132065, A156833 (Mobius transform), A324158, A324159.

Sequence in context: A168341 A083111 A132065 * A180253 A264786 A055225

Adjacent sequences:  A157017 A157018 A157019 * A157021 A157022 A157023

KEYWORD

easy,nonn,look

AUTHOR

R. J. Mathar, Feb 21 2009

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 July 14 16:21 EDT 2020. Contains 335729 sequences. (Running on oeis4.)