A278251 Least number with the prime signature of the n-th central polygonal number.

1, 1, 2, 2, 2, 6, 2, 2, 6, 2, 6, 6, 6, 2, 6, 2, 2, 30, 2, 8, 6, 2, 2, 12, 6, 2, 30, 6, 2, 6, 6, 12, 6, 6, 2, 6, 6, 6, 30, 2, 6, 6, 2, 6, 6, 6, 6, 30, 6, 6, 30, 2, 6, 6, 6, 2, 30, 6, 2, 30, 2, 6, 30, 2, 6, 30, 6, 2, 60, 12, 2, 6, 2, 6, 6, 30, 2, 6, 2, 2, 60, 2, 30, 6, 6, 6, 6, 6, 30, 30, 2, 2, 6, 6, 6, 30, 6, 6, 6, 6, 2, 210, 2, 30, 6, 6, 2, 30, 30, 6, 30, 2, 2

Offset

0,3

Comments

Almost all terms seem to be primorials, 4871 of the first 5212, in other words, most terms of A002061 (in the same range) are squarefree.

Links

Antti Karttunen, Table of n, a(n) for n = 0..5211

Formula

a(n) = A046523(A002061(n)).

Prog

(Scheme) (define (A278251 n) (A046523 (A002061 n)))

Crossrefs

Cf. A002061, A046523.

Cf. also A278246, A278247, A278253.

Sequence in context: A167568 A361301 A240501 * A286847 A291439 A023957

Adjacent sequences: A278248 A278249 A278250 * A278252 A278253 A278254

Keyword

nonn

Author

Antti Karttunen, Nov 21 2016

Status

approved