login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A308672 a(n) = Sum_{d|n} d^(d^3). 1
1, 257, 7625597484988, 340282366920938463463374607431768211713, 2350988701644575015937473074444491355637331113544175043017503412556834518909454345703126 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
The next term (a(6)) has 169 digits. - Harvey P. Dale, Sep 08 2020
LINKS
FORMULA
L.g.f.: -log(Product_{k>=1} (1 - x^k)^(k^(k^3-1))) = Sum_{k>=1} a(k)*x^k/k.
MATHEMATICA
Table[Total[Divisors[n]^Divisors[n]^3], {n, 5}] (* Harvey P. Dale, Sep 08 2020 *)
a[n_] := DivisorSum[n, #^(#^3) &]; Array[a, 5] (* Amiram Eldar, May 11 2021 *)
PROG
(PARI) {a(n) = sumdiv(n, d, d^d^3)}
(PARI) N=10; x='x+O('x^N); Vec(x*deriv(-log(prod(k=1, N, (1-x^k)^(k^(k^3-1))))))
CROSSREFS
Column k=3 of A308674.
Sequence in context: A275098 A194155 A238614 * A308675 A121237 A161683
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 16 2019
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 18 22:18 EDT 2024. Contains 371782 sequences. (Running on oeis4.)