|
%I #7 Aug 18 2023 18:51:14
%S 1,3,12,60,360,2418,12544,58311,299520,2235324,14515200,122882760,
%T 1152592896,8365593600,81041688000,812657664000,8244072345600,
%U 78851793162240,701965262389248,5040363458592000,49476663690854400
%N a(n) = sigma(2*a(n-1)) for n>1 with a(1)=1.
%H Paul D. Hanna, <a href="/A180707/b180707.txt">Table of n, a(n) for n = 1..400</a>
%t NestList[DivisorSigma[1,2#]&,1,20] (* _Harvey P. Dale_, Jan 12 2018 *)
%o (PARI) a(n)=if(n==1,1,sigma(2*a(n-1)))
%K nonn
%O 1,2
%A _Paul D. Hanna_, Sep 18 2010
|
