A081620 Least m with n*(n+1)/2 divisors.

1, 4, 12, 48, 144, 576, 960, 1260, 3600, 82944, 46080, 184320, 2985984, 129600, 55440, 6881280, 14745600, 58982400, 106168320, 907200, 18662400, 247669456896, 1321205760, 2494800, 207360000, 45158400, 7761600, 978447237120, 543581798400, 2174327193600, 1014686023680

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Formula

A000005(a(n)) = A000217(n) and A000005(k) <> n*(n+1)/2 for k < a(n).

a(n) = A005179(A000217(n)) = A005179(n*(n+1)/2).

Crossrefs

Subsequence of A081619.

Cf. A000005, A000217, A005179.

Sequence in context: A255230 A253087 A262414 * A282023 A149376 A149377

Adjacent sequences: A081617 A081618 A081619 * A081621 A081622 A081623

Keyword

nonn

Author

Reinhard Zumkeller, Mar 24 2003

Extensions

More terms from David Wasserman, Jun 14 2004

a(29)-a(31) from Amiram Eldar, Apr 09 2024

Status

approved