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A061900 Triangular numbers that are not squarefree. 2
28, 36, 45, 120, 136, 153, 171, 276, 300, 325, 351, 378, 496, 528, 630, 666, 780, 820, 990, 1035, 1128, 1176, 1225, 1275, 1431, 1485, 1540, 1596, 1953, 2016, 2080, 2556, 2628, 2775, 2850, 3160, 3240, 3321, 3828, 3916, 4005, 4095, 4560, 4656, 4753, 4851 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

EXAMPLE

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

PROG

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

CROSSREFS

Cf. A000217, A061304.

Sequence in context: A167308 A303261 A168106 * A048023 A105710 A192226

Adjacent sequences:  A061897 A061898 A061899 * A061901 A061902 A061903

KEYWORD

nonn

AUTHOR

Asher Auel (asher.auel(AT)reed.edu), May 20 2001

STATUS

approved

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Last modified June 6 13:01 EDT 2020. Contains 334827 sequences. (Running on oeis4.)