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 A138342 #22 Dec 15 2020 09:07:44
%S A138342 1,9,1,89,1,9,1,889,1,9,1,89,1,9,1,8889,1,9,1,89,1,9,1,889,1,9,1,89,1,
%T A138342 9,1,88889,1,9,1,89,1,9,1,889,1,9,1,89,1,9,1,8889,1,9,1,89,1,9,1,889,
%U A138342 1,9,1,89,1,9,1,888889,1,9,1,89,1,9,1,889,1,9,1,89,1,9,1,8889,1,9,1,89,1,9
%N A138342 First differences of A007088.
%H A138342 Antti Karttunen, <a href="/A138342/b138342.txt">Table of n, a(n) for n = 1..16383</a>
%F A138342 a(n) = A059482(A007814(n)).
%F A138342 From _Antti Karttunen_, Nov 06 2018: (Start)
%F A138342 a(n) = A007088(n) - A007088(n-1).
%F A138342 Multiplicative with a(2^e) = A059482(e), a(p^e) = 1 for odd primes p.
%F A138342 (End)
%F A138342 G.f.: Sum_{k>=0} 10^k * x^(2^k) / (1 + x^(2^k)). - _Ilya Gutkovskiy_, Dec 14 2020
%e A138342 1-0 = 1, 10-1 = 9, 11-10 = 1, 100-11 = 89, ...
%t A138342 Differences[Table[FromDigits[IntegerDigits[n,2]],{n,0,90}]] (* _Harvey P. Dale_, Feb 26 2012 *)
%o A138342 (PARI)
%o A138342 A007088(n) = fromdigits(binary(n), 10); \\ From A007088.
%o A138342 A138342(n) = (A007088(n) - A007088(n-1)); \\ _Antti Karttunen_, Nov 06 2018
%o A138342 (PARI)
%o A138342 A059482(n) = ((10^n)*(1000/1125) + (1/9));
%o A138342 A138342(n) = { my(f=factor(n)); prod(i=1,#f~,if(2==f[i,1],A059482(f[i,2]),1)); }; \\ _Antti Karttunen_, Nov 06 2018
%Y A138342 Cf. A007088, A007814, A059482.
%K A138342 nonn,mult
%O A138342 1,2
%A A138342 Jaume Simon Gispert (jaume(AT)nuem.com), May 17 2008
%E A138342 Offset corrected and keyword:mult added by _Antti Karttunen_, Nov 06 2018