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A072230
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n! (mod n^2), that is, n factorial modulo n^2.
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1
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0, 2, 6, 8, 20, 0, 42, 0, 0, 0, 110, 0, 156, 0, 0, 0, 272, 0, 342, 0, 0, 0, 506, 0, 0, 0, 0, 0, 812, 0, 930, 0, 0, 0, 0, 0, 1332, 0, 0, 0, 1640, 0, 1806, 0, 0, 0, 2162, 0, 0, 0, 0, 0, 2756, 0, 0, 0, 0, 0, 3422, 0, 3660, 0, 0, 0, 0, 0, 4422, 0, 0, 0, 4970, 0, 5256, 0, 0, 0, 0, 0, 6162
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| With the exception of n=4, if n is composite, a(n) = 0. If n is prime, a(n) = n*(n-1). For example, a(11) = 11*10 = 110, a(41)= 41*40 = 1640. [From Gary Detlefs (gdetlefs(AT)aol.com), May 01 2010]
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FORMULA
| fact(n) mod square(n)
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CROSSREFS
| Sequence in context: A103015 A098092 A106164 * A028332 A183171 A124827
Adjacent sequences: A072227 A072228 A072229 * A072231 A072232 A072233
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KEYWORD
| nonn
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AUTHOR
| Roman Stawski (roman.stawski(AT)wanadoo.fr), Jul 05 2002
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