A330446 Composite numbers k such that 2^(k-1) == - lambda(k) (mod k), where lambda is the Carmichael lambda function (A002322).

140, 1054, 1068, 4844, 11209, 19856, 24949, 28390, 78184, 423796, 769516, 4283544, 5935168, 13116053, 122189752, 441252296, 528500308, 636697392, 669629030, 669778082, 1228748591

Offset

1,1

Comments

Composite numbers k such that A062173(k) = A277127(k).

The odd terms are 11209, 24949, 13116053, ...

Note that if p is an odd prime, then 2^(p-1) == - lambda(p) (mod p), because lambda(p) = p-1.

Links

Table of n, a(n) for n=1..21.

Example

140 is a term since it is composite and 2^(140-1) == 140 - lambda(140) == 128 (mod 140).

Mathematica

Select[Range[10^6], CompositeQ[#] && PowerMod[2, # - 1, #] == # - CarmichaelLambda[#] &]

Crossrefs

Cf. A002322, A062173, A277127.

Sequence in context: A184386 A184378 A180294 * A317984 A133711 A184377

Adjacent sequences: A330443 A330444 A330445 * A330447 A330448 A330449

Keyword

nonn,more

Author

Amiram Eldar and Thomas Ordowski, Dec 15 2019

Status

approved