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A280531 a(n) = A049501(A000142(n)).

%I A280531 #11 Jan 06 2017 07:44:58
%S A280531 0,0,1,2,2,4,11,16,16,25,30,64,39,83,111,139,139,165,205,242,283,320,
%T A280531 336,474,440,395,637,655,886,842,1019,1159,1159,1153,1327,1366,1328,
%U A280531 1243,1487,1756,1623,2362,2394,2274,2487,2642,2907,2843,3211,3049,3736
%N A280531 a(n) = A049501(A000142(n)).
%C A280531 a(n) is the major index (1st definition) of n!.
%H A280531 Indranil Ghosh, <a href="/A280531/b280531.txt">Table of n, a(n) for n = 0..10000</a>
%e A280531 For n=4, A000142(n) = 24 and A049501(24) = 2. So a(n) = 2.
%o A280531 (Python)
%o A280531 import math
%o A280531 def M(n):
%o A280531     x=bin(int(n))[2:]
%o A280531     s=0
%o A280531     for i in range(1,len(x)):
%o A280531         if x[i-1]=="1" and x[i]=="0":
%o A280531             s+=i
%o A280531     return s
%o A280531 a=lambda n: M(math.factorial(n))
%Y A280531 Cf. A000142, A049501.
%Y A280531 Cf. A280062 (Major index (2nd definition) of n!).
%K A280531 nonn
%O A280531 0,4
%A A280531 _Indranil Ghosh_, Jan 04 2017