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A119356 Square pyramidal number (A000330) n(n+1)(2n+1)/6 is square-free. +0
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1, 2, 3, 4, 5, 6, 9, 10, 11, 14, 17, 18, 19, 20, 21, 22, 28, 29, 30, 33, 34, 35, 36, 38, 41, 42, 43, 44, 45, 46, 51, 52, 57, 58, 59, 61, 65, 66, 68, 69, 70, 76, 77, 78, 82, 83, 85, 86, 89, 90, 91, 92, 93, 101, 102, 105, 106, 109, 110, 113, 114, 115, 116, 117, 118, 123, 126 (list; graph; listen)
OFFSET

1,2

EXAMPLE

10 is OK because 10*11*(2*10+1)/6 = 5*7*11 is square-free

CROSSREFS

Cf. A000330, A005117.

Sequence in context: A136250 A134697 A032975 this_sequence A137582 A116965 A123054

Adjacent sequences: A119353 A119354 A119355 this_sequence A119357 A119358 A119359

KEYWORD

nonn

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), May 16 2006

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.


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