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 A061900 Triangular numbers that are not squarefree. 2

%I #10 Oct 27 2023 22:00:46

%S 28,36,45,120,136,153,171,276,300,325,351,378,496,528,630,666,780,820,

%T 990,1035,1128,1176,1225,1275,1431,1485,1540,1596,1953,2016,2080,2556,

%U 2628,2775,2850,3160,3240,3321,3828,3916,4005,4095,4560,4656,4753,4851

%N Triangular numbers that are not squarefree.

%H Harry J. Smith, <a href="/A061900/b061900.txt">Table of n, a(n) for n = 1..1000</a>

%e 36 and 45 are triangular numbers (A000217) and are not squarefree: 36 = (2^2)(3^2), 45 = (3^2)(5).

%o (PARI) { n=t=0; for (i=1, 1926, t+=i; if (!issquarefree(t), write("b061900.txt", n++, " ", t)) ) } \\ _Harry J. Smith_, Jul 28 2009

%Y Cf. A000217, A061304.

%K nonn

%O 1,1

%A _Asher Auel_, May 20 2001

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Last modified December 7 05:10 EST 2023. Contains 367629 sequences. (Running on oeis4.)