A306552 Expansion of the 10-adic cube root of -1/7, that is, the 10-adic integer solution to x^3 = -1/7.
3, 9, 5, 5, 4, 0, 3, 8, 3, 9, 1, 6, 4, 7, 2, 6, 5, 2, 9, 6, 2, 4, 5, 7, 0, 0, 9, 0, 6, 1, 9, 3, 8, 2, 5, 1, 4, 1, 8, 4, 1, 0, 2, 4, 4, 7, 8, 5, 0, 6, 2, 4, 3, 8, 4, 2, 0, 2, 4, 7, 3, 3, 4, 7, 1, 9, 9, 3, 5, 3, 9, 7, 0, 4, 4, 6, 3, 7, 7, 1, 7, 6, 3, 5, 5, 9, 6
Offset: 1
Examples
3^3 == 7 == -1/7 (mod 10). 93^3 == 57 == -1/7 (mod 100). 593^3 == 857 == -1/7 (mod 1000). 5593^3 == 2857 == -1/7 (mod 10000). ... ...619383045593^3 = ...142857142857 = ...999999999999/7 = -1/7.
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Crossrefs
10-adic cube root of p/q:
q=7: this sequence (p=-1), A319739 (p=1);
Programs
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Maple
op([1, 3], padic:-rootp(7*x^3+1, 10, 100)); # Robert Israel, Mar 31 2019
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PARI
seq(n)={Vecrev(digits(lift(chinese( Mod((-1/7 + O(5^n))^(1/3), 5^n), Mod((-1/7 + O(2^n))^(1/3), 2^n)))), n)} \\ Following Andrew Howroyd's code for A319740.
Formula
a(n) = 9 - A319739(n) for n >= 2.
Comments