A361671 Squarefree part of the n-th tetrahedral number.

1, 1, 10, 5, 35, 14, 21, 30, 165, 55, 286, 91, 455, 35, 170, 51, 969, 285, 1330, 385, 1771, 506, 23, 26, 13, 91, 406, 1015, 4495, 310, 341, 374, 6545, 1785, 7770, 2109, 9139, 2470, 2665, 2870, 12341, 3311, 14190, 3795, 16215, 1081, 94, 1, 17, 221, 23426, 689, 2915, 770, 7315, 7714, 32509, 8555

Offset

1,3

Links

Table of n, a(n) for n=1..58.

Formula

a(n) = A007913(A000292(n)).

Prog

(Python)
from sympy.ntheory.factor_ import core
def A361671(n): return core(n*(n*(n + 3) + 2)//6) # Chai Wah Wu, Mar 20 2023
(PARI) a(n) = core(n*(n+1)*(n+2)/6); \\ Michel Marcus, Mar 22 2023

Crossrefs

Cf. A007913, A000292, A361670 (of triangular), A083481 (of oblong).

Cf. A003556 (squarefree part is 1).

Sequence in context: A046797 A147675 A070291 * A183132 A141321 A146266

Adjacent sequences: A361668 A361669 A361670 * A361672 A361673 A361674

Keyword

nonn,easy

Author

R. J. Mathar, Mar 20 2023

Status

approved