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%I #4 Apr 28 2018 11:46:06
%S 1,3,13,98,1026,16940,318402,8751951,138772480,4323245864,
%T 120795955200,5325759445800,253615827548160,17175333492928512,
%U 1074413211620474880,76931332113306746880,5820049307236627906560,433263727052606574415872
%N a(n) = sigma(n*a(n-1)) for n>1 with a(1)=1.
%t nxt[{n_,a_}]:={n+1,DivisorSigma[1,a(n+1)]}; NestList[nxt,{1,1},20][[All,2]] (* _Harvey P. Dale_, Apr 28 2018 *)
%o (PARI) a(n)=if(n==1,1,sigma(n*a(n-1)))
%Y Cf. A119791.
%K nonn
%O 1,2
%A _Paul D. Hanna_, Sep 18 2010
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