A030995 - OEIS

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

%S 5,25,625,5625,65625,765625,4765625,34765625,134765625,3134765625,

%T 13134765625,213134765625,2213134765625,62213134765625,

%U 362213134765625,7362213134765625,17362213134765625

%N 9-automorphic numbers ending in 5: final digits of 9*n^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 9*a(n) - 1 is divisible by 2^n. - _Eric M. Schmidt_, Aug 18 2012

%H Eric M. Schmidt, <a href="/A030995/b030995.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(9, 2^n), 0, 2^n, 5^n) for n in range(1, 1001)] # _Eric M. Schmidt_, Aug 18 2012

%K nonn,base,changed

%O 1,1

%A _Eric W. Weisstein_