A291961 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

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

(list; graph; refs; listen; history; text; internal format)

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