A303791 Carmichael numbers (A002997) that are central polygonal numbers (A002061).

5310721, 2278677961, 9593125081, 29859667201, 467593730289953281, 98538479002618905601, 146842414757227736821

Offset

1,1

Comments

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 10^22.

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

Links

Table of n, a(n) for n=1..7.

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

Crossrefs

Intersection of A002997 and A002061.

Cf. A265285, A265628.

Sequence in context: A184782 A116105 A116128 * A058252 A147528 A338542

Adjacent sequences: A303788 A303789 A303790 * A303792 A303793 A303794

Keyword

nonn,more,hard

Author

Max Alekseyev, Apr 30 2018

Extensions

a(6)-a(7) calculated using data from Claude Goutier and added by Amiram Eldar, Apr 20 2024

Status

approved