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a(1) = 2, a(n+1) = a(n)*{tau(a(n))}.
2

%I #7 Apr 23 2023 17:22:52

%S 2,4,12,72,864,20736,933120,117573120,42326323200,36315985305600,

%T 146426052752179200,1475974611741966336000,37784950060594338201600000,

%U 2031318915257551621718016000000,212719716805770805826310635520000000

%N a(1) = 2, a(n+1) = a(n)*{tau(a(n))}.

%C a(1) = 1, a(n+1) = a(n) + tau(a(n)) gives A064491.

%e a(4) = 72 and tau(72)= 12, hence a(5) = 72*12= 864.

%t NestList[# DivisorSigma[0,#]&,2,20] (* _Harvey P. Dale_, Apr 23 2023 *)

%o (PARI) for(n=1,16,if(n==1,a=2,a*=numdiv(a)); print(a); )

%Y Cf. A064491.

%K nonn

%O 1,1

%A _Amarnath Murthy_, Jul 06 2003

%E More terms from _Ray Chandler_, Jul 16 2003