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!)
A180708 a(n) = sigma(3*a(n-1)) for n>1 with a(1)=1. 1
1, 4, 28, 224, 2016, 20160, 243840, 2545920, 30905280, 388908036, 3622707200, 44117911764, 387754160640, 5065246517760, 67333642371072, 829993839244416, 9887956143636480, 150394118343146496, 1797812804753817600 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
MATHEMATICA
NestList[DivisorSigma[1, 3#]&, 1, 20] (* Harvey P. Dale, Aug 18 2023 *)
PROG
(PARI) a(n)=if(n==1, 1, sigma(3*a(n-1)))
CROSSREFS
Cf. A180707.
Sequence in context: A121203 A368234 A192620 * A370187 A191094 A220876
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Sep 18 2010
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 March 28 17:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)