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A063506
a(n) = phi(a(n-1)) * number of divisors of a(n-1), a(1)=3.
1
3, 4, 6, 8, 16, 40, 128, 512, 2560, 20480, 212992, 2949120, 80216064, 3019898880, 130459631616, 7827577896960, 935134639423488, 128247036263792640, 22024291027701989376, 7222873082376801484800, 4118350906606118082969600
OFFSET
1,1
LINKS
MATHEMATICA
NestList[EulerPhi[#]DivisorSigma[0, #]&, 3, 20] (* Harvey P. Dale, Mar 10 2019 *)
PROG
(PARI) s(n)=if(n<2, n+2, eulerphi(s(n-1))*numdiv(s(n-1)) ); for(n=1, 22, print(s(n)))
(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
CROSSREFS
Sequence in context: A204659 A134580 A007749 * A084438 A186700 A350217
KEYWORD
nonn
AUTHOR
Jason Earls, Aug 09 2001
STATUS
approved