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A309605
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Digits of the 10-adic integer (61/9)^(1/3).
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3
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9, 0, 5, 0, 5, 4, 7, 1, 9, 1, 6, 0, 9, 8, 5, 7, 1, 0, 7, 3, 1, 0, 9, 5, 1, 4, 9, 9, 5, 7, 9, 3, 0, 1, 1, 9, 0, 1, 4, 1, 4, 0, 6, 4, 4, 1, 8, 0, 0, 1, 7, 6, 9, 1, 5, 3, 8, 1, 4, 2, 6, 7, 1, 3, 3, 9, 8, 0, 4, 5, 3, 7, 2, 5, 2, 7, 5, 5, 4, 6, 1, 0, 0, 2, 2, 3, 2, 0, 7, 3, 4, 2, 7, 7, 1, 0, 3, 1, 0, 9
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OFFSET
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0,1
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LINKS
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FORMULA
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Define the sequence {b(n)} by the recurrence b(0) = 0 and b(1) = 9, b(n) = b(n-1) + 7 * (9 * b(n-1)^3 - 61) mod 10^n for n > 1, then a(n) = (b(n+1) - b(n))/10^n.
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EXAMPLE
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9^3 == 9 (mod 10).
9^3 == 29 (mod 10^2).
509^3 == 229 (mod 10^3).
509^3 == 2229 (mod 10^4).
50509^3 == 22229 (mod 10^5).
450509^3 == 222229 (mod 10^6).
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PROG
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(PARI) N=100; Vecrev(digits(lift(chinese(Mod((61/9+O(2^N))^(1/3), 2^N), Mod((61/9+O(5^N))^(1/3), 5^N)))), N)
(Ruby)
ary = [9]
a = 9
n.times{|i|
b = (a + 7 * (9 * a ** 3 - 61)) % (10 ** (i + 2))
ary << (b - a) / (10 ** (i + 1))
a = b
}
ary
end
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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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