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A246133
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Binomial(2n, n) - 2 mod n^3.
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6
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0, 4, 18, 4, 0, 58, 0, 68, 504, 754, 0, 1562, 0, 2062, 2518, 580, 0, 922, 0, 818, 6535, 7990, 0, 12058, 250, 4398, 2691, 10358, 0, 12422, 0, 16964, 10666, 29482, 3680, 42818, 0, 41158, 19791, 13618, 0, 54430, 0, 71942, 40993, 73006, 0, 12058, 3430, 122254, 98278, 127494, 0
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OFFSET
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1,2
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COMMENTS
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When e=3, the numbers binomial(2n, n) - 2 mod n^e are 0 whenever n is a prime greater than 3 (Wolstenholme's theorem; see A246130 for introductory comments). No composite number n for which a(n)=0 was found up to n=431500 (conjecture: there are none, and a(n)=0 for n>3 is a deterministic primality test).
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LINKS
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FORMULA
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For any prime p>3, a(p)=0.
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EXAMPLE
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a(7)= (binomial(14,7)-2) mod 7^3 = (3432-2) mod 343 = 10*343 mod 343 = 0.
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MAPLE
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seq(binomial(2*n, n)-2 mod n^3, n=1..100); # Robert Israel, Aug 17 2014
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PROG
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(PARI) a(n) = (binomial(2*n, n)-2)%n^3
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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