A123101 -id:A123101 - cp's OEIS frontend

A173941 Numbers k such that tau(lambda(k)) = lambda(tau(k)).

1, 2, 4, 6, 8, 12, 24, 100, 168, 180, 264, 300, 468, 552, 684, 1100, 1128, 1260, 1416, 1848, 1992, 2340, 2568, 3276, 3300, 3600, 3864, 4008, 4296, 4788, 4920, 5208, 5448, 6072, 6312, 7056, 7224, 7896, 8184, 8328, 8616, 9192, 9912

Offset: 1

Michel Lagneau, Nov 26 2010

nonn

Previous name: tau(lambda(n)) = lambda(tau(n)) for the sequential application of the number of divisors of n and Carmichael lambda function.

Numbers k such that A000005(A002322(k)) = A002322(A000005(k)).

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A000005, A002322, A123101.

with(numtheory): for n from 1 to 10000 do:if tau(lambda(n))=lambda(tau(n))then
  printf(`%d, `,n):else fi:od:

Cases[Range[1000], k_ /; DivisorSigma[0,CarmichaelLambda[k]] == CarmichaelLambda[DivisorSigma[0,k]]]

lambda(n) = lcm(znstar(n)[2]); \\ A002322
isok(k) = numdiv(lambda(k)) == lambda(numdiv(k)); \\ Michel Marcus, Jul 17 2019

Name edited by Michel Marcus, Mar 18 2016

A173942 Numbers n such that sigma(lambda(n)) = lambda(sigma(n)).

Original entry on oeis.org

1, 9, 18, 36, 63, 72, 126, 252, 504, 712, 729, 1458, 1716, 2136, 2916, 2982, 3484, 3588, 4402, 5103, 5467, 5832, 7120, 7332, 8800, 9798, 9894, 10206, 10452, 11928, 12948, 13192, 13851, 14952, 17420, 17608, 17963

Offset: 1

Michel Lagneau, Nov 26 2010

nonn

Previous name: sigma(lambda(n)) = lambda(sigma(n)) for the sequential application of the sum of divisors of n and Carmichael lambda functions.

Numbers n such that A000203(A002322(n))=A002322(A000203(n)).

			36 is in the sequence because:
sigma(lambda(36)) = sigma(6) = 12,
lambda(sigma(36)) = lambda(91) = 12.

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A123101, A002322.

with(numtheory): for n from 1 to 20000 do:if sigma(lambda(n))=lambda(sigma(n))then
  printf(`%d, `,n):else fi:od:

Cases[Range[20000], k_ /; DivisorSigma[1,CarmichaelLambda[k]] == CarmichaelLambda[DivisorSigma[1,k]]]

Name edited by Michel Marcus, Mar 18 2016

cp's OEIS Frontend

A173941 Numbers k such that tau(lambda(k)) = lambda(tau(k)).

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