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URL: https://oeis.org/A180708

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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
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