A280531 - OEIS

%I #11 Jan 06 2017 07:44:58

%S 0,0,1,2,2,4,11,16,16,25,30,64,39,83,111,139,139,165,205,242,283,320,

%T 336,474,440,395,637,655,886,842,1019,1159,1159,1153,1327,1366,1328,

%U 1243,1487,1756,1623,2362,2394,2274,2487,2642,2907,2843,3211,3049,3736

%N a(n) = A049501(A000142(n)).

%C a(n) is the major index (1st definition) of n!.

%H Indranil Ghosh, <a href="/A280531/b280531.txt">Table of n, a(n) for n = 0..10000</a>

%e For n=4, A000142(n) = 24 and A049501(24) = 2. So a(n) = 2.

%o (Python)

%o import math

%o def M(n):

%o     x=bin(int(n))[2:]

%o     s=0

%o     for i in range(1,len(x)):

%o         if x[i-1]=="1" and x[i]=="0":

%o             s+=i

%o     return s

%o a=lambda n: M(math.factorial(n))

%Y Cf. A000142, A049501.

%Y Cf. A280062 (Major index (2nd definition) of n!).

%K nonn

%O 0,4

%A _Indranil Ghosh_, Jan 04 2017