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 A063506 a(n) = phi(a(n-1)) * number of divisors of a(n-1), a(1)=3. 1

%I

%S 3,4,6,8,16,40,128,512,2560,20480,212992,2949120,80216064,3019898880,

%T 130459631616,7827577896960,935134639423488,128247036263792640,

%U 22024291027701989376,7222873082376801484800,4118350906606118082969600

%N a(n) = phi(a(n-1)) * number of divisors of a(n-1), a(1)=3.

%H Harry J. Smith, <a href="/A063506/b063506.txt">Table of n, a(n) for n = 1..148</a>

%t NestList[EulerPhi[#]DivisorSigma[0,#]&,3,20] (* _Harvey P. Dale_, Mar 10 2019 *)

%o (PARI) s(n)=if(n<2,n+2,eulerphi(s(n-1))*numdiv(s(n-1)) ); for(n=1,22,print(s(n)))

%o (PARI) { for (n=1, 148, if (n>1, a=eulerphi(a)*numdiv(a), a=3); write("b063506.txt", n, " ", a) ) } \\ _Harry J. Smith_, Aug 24 2009

%K nonn

%O 1,1

%A _Jason Earls_, Aug 09 2001

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Last modified August 14 09:14 EDT 2020. Contains 336480 sequences. (Running on oeis4.)