%I A133033
%S A133033 3,5,9,13,25,33,37,61,121,177,213,253,1041,1213,2557,4405,4561,6433,
%T A133033 8505,8845,19377,19881,22425,39873,43401,46417,88993,172485,221005,
%U A133033 264097,432181,1513677,1718865,2515573,2796537,5952441,6042753,13945185
%N A133033 Number of proper divisors of n-th even perfect number.
%C A133033 Perfect numbers: A000396(n) = 2^a(n) - 2^A090748(n), assuming there are 
               no odd perfect numbers.
%C A133033 Also, a(n) is equal to the number of bits in A135650(n), the n-th even 
               perfect number written in base 2.
%H A133033 C. K. Caldwell, "Top Twenty" page, <a href="http://www.utm.edu/research/
               primes/lists/top20/Mersenne.html">Mersenne Primes</a>.
%H A133033 O. E. Pol, <a href="http://www.polprimos.com">Determinacion geometrica 
               de los numeros primos y perfectos</a>.
%F A133033 a(n) = A061645(n) - 1, assuming there are no odd perfect numbers.
%F A133033 a(n) = A000043(n) + A090748(n) = 2*A000043(n) - 1 = 2*A090748(n) + 1.
%Y A133033 Cf. A135650.
%Y A133033 Sequence in context: A052282 A001993 A153263 this_sequence A145365 A146433 
               A134672
%Y A133033 Adjacent sequences: A133030 A133031 A133032 this_sequence A133034 A133035 
               A133036
%K A133033 nonn
%O A133033 1,1
%A A133033 Omar E. Pol (info(AT)polprimos.com), Oct 27 2007, Feb 23 2008, Apr 28 
               2009