This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A288351 #17 Jun 10 2017 16:35:26 %S A288351 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 A288351 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 A288351 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 %N A288351 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 A288351 For definitions and comments see A288350. %C A288351 It is conjectured that a(n)=0 for n>=8. %C A288351 The conjecture is true, as shown in the corresponding comment in A288350. - _Hugo Pfoertner_, Jun 09 2017 %e A288351 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 A288351 Cf. A288350, A288352, A288353, A288354, A288355, A288356. %K A288351 nonn %O A288351 1,1 %A A288351 _Hugo Pfoertner_, Jun 08 2017