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A303791 Carmichael numbers (A002997) that are central polygonal numbers (A002061). 1
5310721, 2278677961, 9593125081, 29859667201, 467593730289953281 (list; graph; refs; listen; history; text; internal format)
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 2^64.

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

LINKS

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

CROSSREFS

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

KEYWORD

nonn,more,hard

AUTHOR

Max Alekseyev, Apr 30 2018

STATUS

approved

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Last modified February 22 17:14 EST 2020. Contains 332140 sequences. (Running on oeis4.)