|
|
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
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|