A322933 Digits of the 8-adic integer 7^(1/3).

7, 2, 6, 6, 2, 7, 7, 2, 0, 6, 5, 6, 7, 3, 5, 6, 1, 5, 6, 1, 0, 0, 2, 4, 6, 1, 5, 0, 4, 3, 3, 4, 3, 3, 0, 5, 2, 5, 4, 4, 5, 2, 7, 5, 2, 7, 2, 1, 4, 5, 7, 5, 7, 0, 2, 7, 0, 1, 3, 2, 4, 7, 6, 5, 1, 1, 2, 4, 2, 0, 7, 2, 5, 4, 0, 4, 7, 0, 4, 3, 5, 5, 1, 3, 4, 4, 6, 1, 7, 7, 3, 5, 3, 6, 6, 5, 7, 5, 0, 6

Offset

0,1

Comments

The octal version of A225405.

Links

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

Wikipedia, Hensel's Lemma.

Formula

Define the sequence {b(n)} by the recurrence b(0) = 0 and b(1) = 7, b(n) = b(n-1) + 5 * (b(n-1)^3 - 7) mod 8^n for n > 1, then a(n) = (b(n+1) - b(n))/8^n. - Seiichi Manyama, Aug 14 2019

Example

56027726627^3 == 7 (mod 8^11) in octal.

Prog

(PARI) N=100; Vecrev(digits(lift((7+O(2^(3*N)))^(1/3)), 8), N) \\ Seiichi Manyama, Aug 14 2019
(Ruby)
def A322933(n)
  ary = [7]
  a = 7
  n.times{|i|
    b = (a + 5 * (a ** 3 - 7)) % (8 ** (i + 2))
    ary << (b - a) / (8 ** (i + 1))
    a = b
  }
  ary
end
p A322933(100) # Seiichi Manyama, Aug 14 2019

Crossrefs

Cf. A225405 (decimal version), A322931, A322932.

Sequence in context: A019934 A295874 A182548 * A143306 A199075 A228045

Adjacent sequences: A322930 A322931 A322932 * A322934 A322935 A322936

Keyword

nonn,base,easy

Author

Patrick A. Thomas, Dec 31 2018

Status

approved