%I #14 Jul 31 2019 15:17:08
%S 2,4,18,28,51,71,74,91,96,108,121,124,141,142,146,158,200,220,223,232,
%T 239,243,263,265,271,275,296,312,324,343,345,385,388,392,395,399,418,
%U 426,427,437,439,441,449,467,511
%N Positions of 4's in the decimal expansion of sqrt(2).
%H G. C. Greubel, <a href="/A054300/b054300.txt">Table of n, a(n) for n = 1..10000</a>
%t Flatten[Position[RealDigits[Sqrt[2],10,600][[1]],4]] (* _Harvey P. Dale_, Aug 03 2012 *)
%K nonn,base
%O 1,1
%A _Simon Plouffe_, Feb 20 2000