A361671 - OEIS

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

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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