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A361671
Squarefree part of the n-th tetrahedral number.
2
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
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
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Mar 20 2023
STATUS
approved