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%I #56 Dec 23 2019 18:57:20
%S 0,0,3,1,51,89,11,417,1251,9897,13307,3057,21459,64377,1765995,
%T 1103681,28476867,51876169,21410779,265558929,796676787,5611255833,
%U 8243832907,3256662241,22654888611,67964665833,1028527718331,886559899441,15853819231635,29969271650489
%N The smallest positive number of the form 3^n-2^a-2^b.
%C It follows from a work of Vojta that a(n) tends to infinity as n tends to infinity.
%D P. Vojta, Integral points on varieties. Thesis, Harvard, 1983.
%H Andrew Howroyd, <a href="/A292425/b292425.txt">Table of n, a(n) for n = 1..200</a>
%H Mo Deze and R. Tijdeman, <a href="https://doi.org/10.1016/0019-3577(92)90045-M">Exponential diophantine equations with four terms</a>, Indag. Math. N.S. 3 (1992), 47--57.
%H R. Tijdeman and Lian Xiang Wang, <a href="https://projecteuclid.org/euclid.pjm/1102689800">Sums of products of powers of given prime numbers</a>, Pacific J. Math. 132, (1988), 177--193.
%H Tomohiro Yamada, <a href="https://doi.org/10.1017/S001708950800459X">On the diophantine equation x^m=y^n1+y^n2+...+y^nk</a>, Glasgow Math. J. 51 (2009), 143--148.
%o (PARI) f(x)=x-2^floor(log(x)/log(2)); g(x)=f(f(x)); a(n)=g(3^n)
%o (PARI) a(n)={my(t=3^n); t-=1<<logint(t,2); t-=1<<logint(t,2); t} \\ _Andrew Howroyd_, Dec 23 2019
%Y Cf. A056577 (smallest 3^n-2^k).
%K nonn
%O 1,3
%A _Tomohiro Yamada_, Sep 29 2017
%E Terms a(15) and beyond from _Andrew Howroyd_, Dec 23 2019
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