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Search: id:A135616
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| A135616 |
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Number of permutations p of {1,2,...,n} such that p(x) is a polynomial in x, modulo n, of degree at most 2, for x=1,2,3,...,n. |
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+0
1
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OFFSET
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1,2
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EXAMPLE
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For n=4, the permutation (1,2,3,4) is clearly given by the polynomial p(x)=x, for any modulus and the permutation (1,4,3,2) is found to be given by p(x)=2x^2+x+2 (modulo 4), since 2+1+2=5=1(mod 4), 2*4+2+2=12=0 (mod 4), 2*9+3+2=23=3 (mod 4) and 2*16+4+2=38=2 (mod 4). Among the other 22 permutations of (1,2,3,4) four are found to have the desired property, for a total of 6, so a(4)=6.
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CROSSREFS
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Sequence in context: A111410 A083774 A081518 this_sequence A119551 A100634 A130865
Adjacent sequences: A135613 A135614 A135615 this_sequence A135617 A135618 A135619
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KEYWORD
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nonn
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AUTHOR
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John W. Layman (layman(AT)math.vt.edu), Feb 28 2008
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