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A303791
Carmichael numbers (A002997) that are central polygonal numbers (A002061).
1
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
CROSSREFS
Intersection of A002997 and A002061.
Sequence in context: A184782 A116105 A116128 * A058252 A147528 A338542
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