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(2*16^(5^n) + (10^n)/2 - 1) mod 10^n: a sequence of trimorphic numbers ending (for n > 1) in 1.
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%I #9 Apr 10 2013 02:08:19

%S 6,1,251,3751,68751,718751,9218751,24218751,74218751,8574218751,

%T 13574218751,663574218751,5163574218751,30163574218751,

%U 980163574218751,2480163574218751,37480163574218751,987480163574218751,487480163574218751,65487480163574218751

%N (2*16^(5^n) + (10^n)/2 - 1) mod 10^n: a sequence of trimorphic numbers ending (for n > 1) in 1.

%C a(n) is the unique positive integer less than 10^n such that a(n) + 2^(n-1) + 1 is divisible by 2^n and a(n) - 1 is divisible by 5^n.

%H Eric M. Schmidt, <a href="/A224476/b224476.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) = (A224474(n) + 10^n/2) mod 10^n.

%o (Sage) def A224476(n) : return crt(2^(n-1)-1, 1, 2^n, 5^n)

%Y Cf. A033819. Converges to the 10-adic number A063006. The other trimorphic numbers ending in 1 are included in A199685 and A224474.

%K nonn,base

%O 1,1

%A _Eric M. Schmidt_, Apr 07 2013