A291961 Numbers n > 1 such that 2^lambda(n) == 1 (mod n^2), where lambda(n) is the Carmichael lambda function (A002322).

1093, 3279, 3511, 7651, 10533, 14209, 17555, 22953, 31599, 42627, 45643, 52665, 99463, 136929, 157995, 228215, 298389, 410787, 684645, 2053935, 3837523, 11512569, 19187615, 26862661, 34537707, 49887799, 57562845, 80587983, 134313305, 149663397, 172688535, 241763949, 249438995, 349214593, 402939915, 448990191, 748316985, 1047643779, 1208819745, 1746072965, 2244950955, 3142931337, 5238218895

Offset

1,1

Comments

An alternative generalization of Wieferich primes (A001220).

A subsequence of A077816, since the A002322(n)|A000010(n). The first 12 terms are common.

15714656685 (see A265630) is also a term. - Michel Marcus, Sep 14 2017

Links

Table of n, a(n) for n=1..43.

Mathematica

Select[Range[2, 100000], Divisible[2^CarmichaelLambda[#] - 1, #^2] &]

Prog

(PARI) isok(n) = Mod(2, n^2)^lcm(znstar(n)[2]) == 1; \\ Michel Marcus, Sep 11 2017

Crossrefs

Cf. A265630, A001220, A002322, A077816, A182297, A246503.

Sequence in context: A038469 A246503 A077816 * A001220 A265630 A355545

Adjacent sequences: A291958 A291959 A291960 * A291962 A291963 A291964

Keyword

nonn

Author

Amiram Eldar, Sep 06 2017

Extensions

a(32)-a(36) from Michel Marcus, Sep 11 2017

a(37)-a(41) from Michel Marcus, Sep 12 2017

a(42)-a(43) from Michel Marcus, Sep 14 2017

Status

approved