A086075 - OEIS

%I #10 May 05 2024 19:30:32

%S 0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,0,0,

%T 0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,1,0,0,

%U 1,1,1,0,0,0,0,0,0,0,0,0,1,0,1,1,0,0,1,0,0,1,1,1,1,1,2,1,1,1,1,1,0,0,0,0,1

%N Number of 4's in decimal expansion of triangular number n(n+1)/2.

%H Paolo Xausa, <a href="/A086075/b086075.txt">Table of n, a(n) for n = 0..10000</a>

%t DigitCount[Accumulate[Range[0, 100]], 10, 4] (* _Paolo Xausa_, May 05 2024 *)

%Y Cf. 0's A086071, 1's A086072, 2's A086073, 3's A086074, 5's A086076, 6's A086077, 7's A086078, 8's A086079, 9's A086080.

%K base,nonn

%O 0,95

%A _Jason Earls_, Jul 08 2003