A277720 Numbers k > 2 such that lambda(k)^2 divides k-1, where lambda(k) = A002322(k).

2320690177, 17069520863233, 42182344790209, 65465530560001, 3432376805760001, 13322002122777601, 20388795375960001, 129009714848870401, 580007888606160001, 1096591987029196801, 3029756968906340401, 5806765663003468801, 6213994663149504001, 6367205158826803201, 7802569551798000001, 10319507991273499201

Offset

1,1

Comments

Squarefree numbers k > 2 such that (p-1)^2 | k-1 for every prime p|k.

For the first five terms, lambda(k)^2 | phi(k). - Thomas Ordowski, Apr 11 2017

Links

Amiram Eldar, Table of n, a(n) for n = 1..47 (terms below 10^22, calculated using data from Claude Goutier)

Claude Goutier, Compressed text file carm10e22.gz containing all the Carmichael numbers up to 10^22.

Prog

(PARI) isok(n) = (n % lcm(znstar(n)[2])^2)  == 1; \\ Michel Marcus, Apr 22 2017

Crossrefs

Subsequence of A002997 and of A277389.

Cf. A002322.

Sequence in context: A346363 A022240 A251490 * A333664 A090875 A132907

Adjacent sequences: A277717 A277718 A277719 * A277721 A277722 A277723

Keyword

nonn,changed

Author

Thomas Ordowski and Charles R Greathouse IV, Oct 28 2016

Extensions

a(7)-a(16) from Max Alekseyev, Apr 23 2017

Status

approved