%I A138510
%S A138510 1,2,1,6,8,3,3,12,1,14,12,18,2,20,14,24,1,18,4,20,30,32,4,24,38,4,42,5,
%T A138510 44,30,4,32,48,5,54,38,5,60,5,1,62,42,44,5,68,48,72,2,30,74,32,80,54,5,
%U A138510 84,1,60,90,62,38,3,98,68,102,6,42,104,3,72,108,44,6,110,74,3,114,48,80
%N A138510 Smallest number b such that in base b representation the prime factors 
               of the n-th semiprime (A001358) have equal lengths.
%C A138510 a(n) = 1 iff A001358(n) is a prime square (A001248);
%C A138510 a(A138511(n)) = A084127(A138511(n)) + 1.
%e A138510 n=91=7*13: 7 = '111'[binary] = '21'[ternary] = '13'[base4]
%e A138510 and 13 = '1101'[binary] = '111'[ternary] = '31'[base4],
%e A138510 therefore 91 is a term, a(31) = 91.
%Y A138510 Cf. A078972, A085721.
%Y A138510 Sequence in context: A112007 A113374 A136470 this_sequence A026215 A026220 
               A138750
%Y A138510 Adjacent sequences: A138507 A138508 A138509 this_sequence A138511 A138512 
               A138513
%K A138510 nonn,base
%O A138510 1,2
%A A138510 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 21 2008