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 A135774 #12 Nov 09 2016 02:34:31
%S A135774 1,5,7,11,13,25,49,65,69,74,77,82,85,86,87,91,93,94,95,106,111,115,
%T A135774 118,119,122,123,125,129,133,134,141,142,143,145,146,155,158,159,161,
%U A135774 166,177,178,183,185,187,194,201,202,203,205,206,209,213,214,215,217,218
%N A135774 Numbers having number of divisors equal to number of digits in base 4.
%C A135774 Since 4 is not a prime, no element > 1 of the sequence A000302(k)=4^k (having k+1 digits in base 4 but 2k+1 divisors) can be member of this sequence. However all powers of 5 up to 5^6 are in this sequence, having the same number of digits (in base 4) than the same power of 4 (since (5/4)^6 < 4 < (5/4)^7) and also that number of divisors.
%H A135774 G. C. Greubel, <a href="/A135774/b135774.txt">Table of n, a(n) for n = 1..1000</a>
%e A135774 a(1) = 1 since 1 has 1 divisor and 1 digit (in base 4 as in any other base).
%e A135774 a(2)..a(5) = 5, 7, 11, 13 are the primes (to have 2 divisors {1,p}) between 4 and 4^2 - 1 (to have 2 digits in base 4).
%e A135774 a(6), a(7) = 25, 49 are the squares of primes (3 divisors) between 4^2 = 100[4] and 4^3 - 1 = 333_4.
%e A135774 They are followed by all semiprimes and cubes of primes (4 divisors) between 4^3 and 4^4 - 1.
%t A135774 Select[Range[500], DivisorSigma[0, #] == IntegerLength[#, 4] &] (* _G. C. Greubel_, Nov 08 2016 *)
%o A135774 (PARI) for(d=1,4,for(n=4^(d-1),4^d-1,d==numdiv(n)&print1(n", ")))
%Y A135774 Cf. A135772-A135779, A095862.
%K A135774 base,nonn
%O A135774 1,2
%A A135774 _M. F. Hasler_, Nov 28 2007