A030992 - OEIS

%I #26 Dec 07 2019 12:18:21

%S 8,68,768,2768,72768,872768,3872768,83872768,683872768,1683872768,

%T 11683872768,11683872768,11683872768,20011683872768,820011683872768,

%U 4820011683872768,34820011683872768,534820011683872768

%N 7-automorphic numbers ending in 8: final digits of 7n^2 agree with n.

%C a(n) is the unique positive integer less than 10^n such that a(n) is divisible by 2^n and 7a(n) - 1 is divisible by 5^n. - _Eric M. Schmidt_, Aug 18 2012

%H Eric M. Schmidt, <a href="/A030992/b030992.txt">Table of n, a(n) for n = 1..1000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/AutomorphicNumber.html">Automorphic Number</a>

%H <a href="/index/Ar#automorphic">Index entries for sequences related to automorphic numbers</a>

%H <a href="/index/Fi#final">Index entries for sequences related to final digits of numbers</a>

%o (Sage) [crt(0, inverse_mod(7, 5^n), 2^n, 5^n) for n in range(1, 1001)] # _Eric M. Schmidt_, Aug 18 2012

%K nonn,base

%O 1,1

%A _Eric W. Weisstein_