Mine for 2016 in Bitcoins! PCG.SE New Year's Puzzle 2016
Mathematica, 94

(For[i=0,IntegerDigits[4Hash[#&lt;&gt;ToString@++i,"SHA256"],64]~SequenceCount~{54,52,53,58}&lt;1,];i)&amp;


This function will try positive integers as candidates. It takes over 4 minutes on my laptop to get the correct answer.

%["foo"]
(* 196870 *)


Longer however faster (~5x) implementation makes use of parallelization: 

f[k_]:=
    Do[If[Length@#&gt;0,Return[i+#[[1,1]]]]&amp;@
        Position[ParallelMap[IntegerDigits[4Hash[k&lt;&gt;ToString@#,"SHA256"],64]
            ~SequenceCount~{54,52,53,58}&amp;,i+Range@1*^4],1]
        ,{i,0,∞,1*^4}]