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A263426
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Permutation of the nonnegative integers: [4k+2, 4k+1, 4k, 4k+3, ...].
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1
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2, 1, 0, 3, 6, 5, 4, 7, 10, 9, 8, 11, 14, 13, 12, 15, 18, 17, 16, 19, 22, 21, 20, 23, 26, 25, 24, 27, 30, 29, 28, 31, 34, 33, 32, 35, 38, 37, 36, 39, 42, 41, 40, 43, 46, 45, 44, 47, 50, 49, 48, 51, 54, 53, 52, 55, 58, 57, 56, 59, 62, 61, 60, 63, 66, 65, 64
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OFFSET
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0,1
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COMMENTS
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Fixed points are the odd numbers (A005408).
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LINKS
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FORMULA
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G.f.: (2 - 3*x + 2*x^2 + x^3)/((x - 1)^2*(1 + x^2)).
a(n) = 2*a(n-1) - 2*a(n-2) + 2*a(n-3) - a(n-4) for n>3.
a(n) = n + (1 + (-1)^n)*(-1)^(n*(n+1)/2).
a(n) = 4*floor((n+1)/4) - (n mod 4) + 2.
a(n+1) = a(n) - A132429(n+1)*(-1)^n.
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MAPLE
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A263426:=n->n + (1 + (-1)^n)*(-1)^(n*(n + 1)/2): seq(A263426(n), n=0..80);
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MATHEMATICA
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Table[n + (1 + (-1)^n)*(-1)^(n*(n + 1)/2), {n, 0, 80}]
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PROG
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(Magma) [n+(1+(-1)^n)*(-1)^(n*(n+1) div 2) : n in [0..80]];
(Magma) /* By definition: */ &cat[[4*k+2, 4*k+1, 4*k, 4*k+3]: k in [0..20]]; // Bruno Berselli, Nov 08 2015
(PARI) Vec((2-3*x+2*x^2+x^3)/((x-1)^2*(1+x^2)) + O(x^100)) \\ Altug Alkan, Oct 19 2015
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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