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%I #17 Jun 10 2017 16:35:26
%S 9,72,455,1500,1014,181,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%T 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%U 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
%N Number of strings of n digits from 1...9 such that no formula using the single digits in the given order exists that evaluates to 0.
%C For definitions and comments see A288350.
%C It is conjectured that a(n)=0 for n>=8.
%C The conjecture is true, as shown in the corresponding comment in A288350. - _Hugo Pfoertner_, Jun 09 2017
%e a(1)=9 because 1...9 /=0. a(2)=72, because only the 9 numbers 11, 22, ..., 99 of the 81 two-digit strings can represent 0.
%Y Cf. A288350, A288352, A288353, A288354, A288355, A288356.
%K nonn
%O 1,1
%A _Hugo Pfoertner_, Jun 08 2017
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