1,1

Also, Carmichael numbers of the form k^2 + k + 1.

Also, Carmichael numbers of the form k^2 - k + 1.

There are no other terms below 2^64.

Carmichael numbers m such that 4m - 3 is square. - Thomas Ordowski, Apr 30 2018

Table of n, a(n) for n=1..5.

Intersection of A002997 and A002061.

Cf. A265285, A265628.

Sequence in context: A184782 A116105 A116128 * A058252 A147528 A115960

Adjacent sequences: A303788 A303789 A303790 * A303792 A303793 A303794

nonn,more,hard

Max Alekseyev, Apr 30 2018

approved