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 A135777 #18 Apr 04 2024 14:05:20
%S A135777 1,7,11,13,17,19,23,29,31,37,41,43,47,49,121,169,289,343,346,355,358,
%T A135777 362,365,371,377,381,382,386,391,393,394,395,398,403,407,411,413,415,
%U A135777 417,422,427,437,445,446,447,451,453,454,458,466,469,471,473,478,481
%N A135777 Numbers having number of divisors equal to number of digits in base 7.
%C A135777 Since 7 is a prime, any power 7^k has k+1 divisors { 7^i ; i=0..k } and the same number of digits in base 7; thus the sequence A000420(k)=7^k is a subsequence of this one.
%H A135777 G. C. Greubel, <a href="/A135777/b135777.txt">Table of n, a(n) for n = 1..1250</a>
%H A135777 Abel Jansma, <a href="https://abeljansma.nl/assets/mscThesis.pdf">E_8 Symmetry Structures in the Ising model</a>, Master's thesis, University of Amsterdam, 2018.
%e A135777 a(1) = 1 since 1 has 1 divisor and 1 digit (in base 7 as in any other base).
%e A135777 All other numbers have at least 2 divisors so there are no other members of the sequence below a(2) = 7 = 10_7 having 2 divisors { 1, 7 } and 2 digits in base 7.
%t A135777 Select[Range[500],DivisorSigma[0,#]==IntegerLength[#,7]&] (* _Harvey P. Dale_, Feb 14 2015 *)
%o A135777 (PARI) for(d=1,4,for(n=7^(d-1),7^d-1,d==numdiv(n)&print1(n", ")))
%Y A135777 Cf. A135772-A135779, A095862.
%K A135777 base,nonn
%O A135777 1,2
%A A135777 _M. F. Hasler_, Nov 28 2007