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A226119 Numbers such that sigma(phi(tau(n)))=tau(phi(sigma(n))). 3
1, 6, 36, 64, 105, 114, 135, 1980, 2016, 3072, 5120, 7056, 7840, 9216, 16320, 18720, 18900, 23100, 23622, 24003, 25536, 26088, 26733, 28455, 29078, 29337, 29700, 29760, 30597, 30894, 30912, 31155, 31496, 31758, 32361, 33782, 34020, 34286, 36000, 36036, 36099 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Paolo P. Lava and T. D. Noe, Table of n, a(n) for n = 1..1000 (first 270 terms from Paolo P. Lava)
EXAMPLE
29337 is in the sequence since:
sigma(29337)=49152 -> phi(49152)=16384 -> tau(16384)=15.
tau(29337)=16 -> phi(16)=8 -> sigma(8)=15.
MAPLE
with(numtheory); A226119:=proc(q) local n;
for n from 1 to q do
if sigma(phi(tau(n)))=tau(phi(sigma(n))) then print(n);
fi; od; end: A226119(10^6);
MATHEMATICA
Select[Range[36099], DivisorSigma[1, EulerPhi[DivisorSigma[0, #]]] == DivisorSigma[0, EulerPhi[DivisorSigma[1, #]]] &] (* T. D. Noe, May 28 2013 *)
CROSSREFS
Sequence in context: A208496 A207584 A207590 * A036148 A134639 A069497
KEYWORD
nonn
AUTHOR
Paolo P. Lava, May 27 2013
STATUS
approved

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Last modified May 26 02:36 EDT 2024. Contains 372807 sequences. (Running on oeis4.)