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 A030991 7-automorphic numbers ending in 5: final digits of 7n^2 agree with n. 1

%I

%S 5,75,375,4375,84375,984375,8984375,58984375,458984375,5458984375,

%T 45458984375,845458984375,2845458984375,22845458984375,

%U 322845458984375,2322845458984375,22322845458984375

%N 7-automorphic numbers ending in 5: 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 5^n and 7a(n) - 1 is divisible by 2^n. - _Eric M. Schmidt_, Aug 18 2012

%H Eric M. Schmidt, <a href="/A030991/b030991.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="http://mathworld.wolfram.com/AutomorphicNumber.html">Automorphic Number</a>

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

%K nonn,base

%O 1,1

%A _Eric W. Weisstein_

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Last modified July 18 21:25 EDT 2019. Contains 325144 sequences. (Running on oeis4.)