%I #9 Apr 09 2013 07:46:11
%S 0,25,875,4375,59375,609375,2109375,37109375,287109375,6787109375,
%T 31787109375,581787109375,5081787109375,90081787109375,
%U 240081787109375,8740081787109375,93740081787109375,243740081787109375,2743740081787109375,57743740081787109375
%N (16^(5^n) + (10^n)/2 - 1) mod 10^n: a sequence of trimorphic numbers ending (for n > 1) in 5.
%C a(n) is the unique nonnegative integer less than 10^n such that a(n) + 2^(n-1) + 1 is divisible by 2^n and a(n) is divisible by 5^n.
%H Eric M. Schmidt, <a href="/A224478/b224478.txt">Table of n, a(n) for n = 1..1000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TrimorphicNumber.html">Trimorphic Number</a>
%H <a href="/index/Ar#automorphic">Index entries for sequences related to automorphic numbers</a>
%F a(n) = (A016090(n) + 10^n/2 - 1) mod 10^n.
%o (Sage) def A224478(n) : return crt(2^(n-1)-1, 0, 2^n, 5^n)
%Y Cf. A033819. Converges to the 10-adic number A091663. The other trimorphic numbers ending in 5 are included in A007185, A216093, and A224477.
%K nonn,base
%O 1,2
%A _Eric M. Schmidt_, Apr 07 2013