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URL: https://oeis.org/A180707

⇱ A180707 - OEIS

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A180707
a(n) = sigma(2*a(n-1)) for n>1 with a(1)=1.
2
1, 3, 12, 60, 360, 2418, 12544, 58311, 299520, 2235324, 14515200, 122882760, 1152592896, 8365593600, 81041688000, 812657664000, 8244072345600, 78851793162240, 701965262389248, 5040363458592000, 49476663690854400
OFFSET
1,2
LINKS
MATHEMATICA
NestList[DivisorSigma[1, 2#]&, 1, 20] (* Harvey P. Dale, Jan 12 2018 *)
PROG
(PARI) a(n)=if(n==1, 1, sigma(2*a(n-1)))
CROSSREFS
Sequence in context: A000258 A326242 A070863 * A062569 A089057 A077134
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Sep 18 2010
STATUS
approved