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A225401 10-adic integer x such that x^3 = -7/9. 7
3, 5, 7, 0, 6, 6, 9, 9, 8, 3, 3, 2, 7, 9, 4, 1, 3, 6, 9, 5, 5, 3, 9, 0, 2, 8, 0, 5, 7, 3, 1, 2, 0, 3, 1, 9, 4, 2, 8, 9, 3, 3, 0, 1, 3, 5, 0, 9, 0, 1, 4, 0, 9, 4, 0, 3, 4, 7, 8, 4, 6, 5, 3, 2, 7, 5, 5, 8, 3, 6, 7, 3, 8, 5, 8, 9, 7, 2, 9, 9, 4, 5, 8, 2, 0, 3, 5, 8, 6, 7, 8, 9, 5, 3, 8, 4, 3, 8, 4, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..10000

FORMULA

Define the sequence {b(n)} by the recurrence b(0) = 0 and b(1) = 3, b(n) = b(n-1) + 3 * (9 * b(n-1)^3 + 7) mod 10^n for n > 1, then a(n) = (b(n+1) - b(n))/10^n. - Seiichi Manyama, Aug 13 2019

EXAMPLE

       3^3 == 7      (mod 10).

      53^3 == 77     (mod 10^2).

     753^3 == 777    (mod 10^3).

     753^3 == 7777   (mod 10^4).

   60753^3 == 77777  (mod 10^5).

  660753^3 == 777777 (mod 10^6).

PROG

(PARI) n=0; for(i=1, 100, m=7*(10^i-1)/9; for(x=0, 9, if(((n+(x*10^(i-1)))^3)%(10^i)==m, n=n+(x*10^(i-1)); print1(x", "); break)))

(PARI) N=100; Vecrev(digits(lift(chinese(Mod((-7/9+O(2^N))^(1/3), 2^N), Mod((-7/9+O(5^N))^(1/3), 5^N)))), N) \\ Seiichi Manyama, Aug 05 2019

(Ruby)

def A225401(n)

  ary = [3]

  a = 3

  n.times{|i|

    b = (a + 3 * (9 * a ** 3 + 7)) % (10 ** (i + 2))

    ary << (b - a) / (10 ** (i + 1))

    a = b

  }

  ary

end

p A225401(100) # Seiichi Manyama, Aug 13 2019

CROSSREFS

Cf. A225410, A309600.

Sequence in context: A024601 A173013 A223174 * A085090 A084713 A162538

Adjacent sequences:  A225398 A225399 A225400 * A225402 A225403 A225404

KEYWORD

nonn,base

AUTHOR

Aswini Vaidyanathan, May 07 2013

STATUS

approved

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Last modified June 1 11:49 EDT 2020. Contains 334762 sequences. (Running on oeis4.)