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 A135779 #16 Nov 09 2016 02:34:03
%S A135779 1,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,121,169,289,
%T A135779 361,529,731,734,737,745,746,749,753,755,758,763,766,767,771,778,779,
%U A135779 781,785,789,791,793,794,799,802,803,807,813,815,817
%N A135779 Numbers having number of divisors equal to number of digits in base 9.
%C A135779 Since 9 is not a prime, no element > 1 of the sequence A001019(k)=9^k (having k+1 digits in base 9, but 2k+1 divisors) can be member of this sequence. Also, no power of a prime less than 9 can be in the sequence, since it will always have fewer divisors than digits in base 9. However all powers of 11 up to 11^10 are in this sequence, having the same number of digits (in base 9) than the same power of 9 (since 10 = floor(log(11/9)/log(9))) and also that number of divisors (since 11 is prime).
%H A135779 G. C. Greubel, <a href="/A135779/b135779.txt">Table of n, a(n) for n = 1..1500</a>
%e A135779 a(1) = 1 since 1 has 1 divisor and 1 digit (in base 9 as in any other base).
%e A135779 It is followed by the primes (having 2 divisors {1,p}) between 9 and 9^2 - 1 (to have 2 digits in base 9).
%e A135779 Then come the squares of primes (3 divisors) between 9^2 = 100_9 and 9^3 - 1 = 888_9.
%e A135779 These are followed by all semiprimes and cubes of primes (4 divisors) between 9^3 and 9^4 - 1.
%t A135779 Select[Range[500], DivisorSigma[0, #] == IntegerLength[#, 9] &] (* _G. C. Greubel_, Nov 09 2016 *)
%o A135779 (PARI) for(d=1,4,for(n=9^(d-1),9^d-1,d==numdiv(n)&print1(n", ")))
%Y A135779 Cf. A135772-A135778, A095862.
%K A135779 base,easy,nonn
%O A135779 1,2
%A A135779 _M. F. Hasler_, Nov 28 2007