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%I #11 Mar 04 2020 20:28:39
%S 1,12321,0,12345654321,12321,121,12345654321,0
%N Smallest concatenation 123...(k-1) k (k-1)...321 (a concatenation of natural numbers from 1 to k and back to 1) that is a multiple of 2n-1, or 0 if no such number exists.
%C a(5k+3) = 0. Are there any other values of n such that a(n) = 0?
%C The next value, 2n-1 = 17, has k = 109, for a total of 435 digits and is too large to include. - _Franklin T. Adams-Watters_, Jun 02 2006
%H Jinyuan Wang, <a href="/A077189/b077189.txt">Table of n, a(n) for n = 1..11</a>
%e a(5) = 12321 is a multiple of 9.
%Y Cf. A077180, A077181, A077182, A077183, A077184, A077186, A077188, A077190.
%Y Cf. A120008.
%K nonn,base
%O 1,2
%A _Amarnath Murthy_, Nov 01 2002
%E More terms from _Franklin T. Adams-Watters_, Jun 02 2006
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