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a(n) = A049502(A000142(n)).
3

%I #25 Jan 04 2017 14:11:48

%S 0,0,0,0,0,0,13,16,22,38,47,73,60,127,160,166,194,249,348,345,359,497,

%T 532,682,709,727,1000,887,1312,1155,1297,1934,2069,1722,1796,2148,

%U 2337,1839,2595,2774,2440,3314,3450,3253,3379,3786,4466,4366,4795,5189,5598

%N a(n) = A049502(A000142(n)).

%C a(n) is the major index (2nd definition) of n!.

%H Indranil Ghosh, <a href="/A280062/b280062.txt">Table of n, a(n) for n = 0..10000</a>

%e for n=15, A000142(n) = 1307674368000 and A049502(1307674368000) = 166. So a(n) = 166.

%o (Python)

%o import math

%o def m(N):

%o x=bin(int(N))[2:][::-1]

%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. A049502, A000142.

%K nonn

%O 0,7

%A _Indranil Ghosh_, Jan 04 2017