cp's OEIS Frontend

A387050 Number of entries in the n-th row of Pascal's triangle not divisible by 16.

%I A387050 #6 Aug 19 2025 05:33:45
%S A387050 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,9,18,15,20,17,22,21,24,21,26,
%T A387050 25,28,27,30,30,32,9,18,23,36,21,30,33,40,25,34,35,44,37,42,44,48,21,
%U A387050 42,37,52,37,50,48,56,43,54,52,60,54,60,60,64,9,18,23,36,29
%N A387050 Number of entries in the n-th row of Pascal's triangle not divisible by 16.
%o A387050 (Python)
%o A387050 def A387050(n):
%o A387050     n1 = n>>1
%o A387050     n2 = n1>>1
%o A387050     n3 = n2>>1
%o A387050     np = ~n
%o A387050     n10, n100, n110 = (k1:=n1&np).bit_count(), (k2:=(k1>>1)&np).bit_count(), (k3:=n2&k1).bit_count()
%o A387050     n1100, n1000, n1010, n1110 = (n3&k2).bit_count(), ((k2>>1)&np).bit_count(), ((k1>>2)&k1).bit_count(), (n3&k3).bit_count()
%o A387050     return n10*(n10*(n10+3)+6*((n100<<2)+n110)+20)//6+((n1000<<2)+n100+n1010+n1100<<2)+n110+n1110+8<<n.bit_count()>>3
%Y A387050 Cf. A001316, A006047, A194459, A382720-A382725, A386952.
%K A387050 nonn,new
%O A387050 0,2
%A A387050 _Chai Wah Wu_, Aug 15 2025