%I #23 Feb 16 2025 08:32:35

%S 5,25,125,8125,78125,578125,2578125,42578125,642578125,3642578125,

%T 83642578125,983642578125,1983642578125,51983642578125,

%U 251983642578125,1251983642578125,51251983642578125

%N 5-automorphic numbers: final digits of 5n^2 agree with n.

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

%H Eric M. Schmidt, <a href="/A030988/b030988.txt">Table of n, a(n) for n = 1..1000</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>

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

%o (Sage) [crt(inverse_mod(5, 2^n), 0, 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_