A306828 Carmichael numbers whose index is a power of 2 (see A174590).

7816642561, 49413980161, 32713826587115521

Offset

1,1

Comments

Carmichael numbers m such that (m-1)/lambda(m) = 2^k for some k, namely for k = 13, 13, 14, ...

Composite numbers m for which Od(lambda(m)) = Od(m-1), where Od(m) = A000265(m) is the odd part of m.

By Lehmer's totient conjecture, there are no composite numbers m such that Od(phi(m)) = Od(m-1), where phi(m) = A000010(m) and Od(m) as above.

a(4) > 10^22, if it exists. - Amiram Eldar, Apr 21 2024

Links

Table of n, a(n) for n=1..3.

Crossrefs

Cf. A000010, A000265, A002322, A002997, A174590.

Sequence in context: A225141 A015413 A288090 * A364436 A075131 A250865

Adjacent sequences: A306825 A306826 A306827 * A306829 A306830 A306831

Keyword

nonn,hard,more,bref

Author

Thomas Ordowski, Mar 12 2019

Extensions

a(1)-a(3) from Amiram Eldar, Mar 12 2019

Status

approved