This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A361671 #10 Mar 23 2023 03:45:11 %S A361671 1,1,10,5,35,14,21,30,165,55,286,91,455,35,170,51,969,285,1330,385, %T A361671 1771,506,23,26,13,91,406,1015,4495,310,341,374,6545,1785,7770,2109, %U A361671 9139,2470,2665,2870,12341,3311,14190,3795,16215,1081,94,1,17,221,23426,689,2915,770,7315,7714,32509,8555 %N A361671 Squarefree part of the n-th tetrahedral number. %F A361671 a(n) = A007913(A000292(n)). %o A361671 (Python) %o A361671 from sympy.ntheory.factor_ import core %o A361671 def A361671(n): return core(n*(n*(n + 3) + 2)//6) # _Chai Wah Wu_, Mar 20 2023 %o A361671 (PARI) a(n) = core(n*(n+1)*(n+2)/6); \\ _Michel Marcus_, Mar 22 2023 %Y A361671 Cf. A007913, A000292, A361670 (of triangular), A083481 (of oblong). %Y A361671 Cf. A003556 (squarefree part is 1). %K A361671 nonn,easy %O A361671 1,3 %A A361671 _R. J. Mathar_, Mar 20 2023