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A180516
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Numbers of the form i*4^j-1 (i=1..3, j >= 0).
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11
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0, 1, 2, 3, 7, 11, 15, 31, 47, 63, 127, 191, 255, 511, 767, 1023, 2047, 3071, 4095, 8191, 12287, 16383, 32767, 49151, 65535, 131071, 196607, 262143, 524287, 786431, 1048575, 2097151, 3145727, 4194303, 8388607, 12582911, 16777215, 33554431, 50331647, 67108863, 134217727, 201326591, 268435455, 536870911, 805306367, 1073741823, 2147483647, 3221225471
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) = a(n-1)+4*a(n-3)-4*a(n-4). G.f.: x^2*(x^2+x+1) / ((x-1)*(4*x^3-1)). [Colin Barker, Feb 01 2013]
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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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