%I
%S 0,1,1,2,3,2,2,4,3,4,7,5,6,5,5,4,6,4,4,8,6,8,8,7,6,10,7,8,15,11,14,10,
%T 12,10,13,11,12,11,11,10,12,10,10,11,9,8,14,10,12,10,10,8,12,8,8,16,
%U 12,16,13,14,12,17,14,16,18,16,16,17,15,14,17,13,12,22,16,20,18,17,14,22
%N Mod 3 analog of Stern's diatomic series.
%C Essentially diagonal sums of Pascal's triangle modulo 3.
%H G. C. Greubel, <a href="/A098534/b098534.txt">Table of n, a(n) for n = 0..10000</a>
%F a(n) = Sum_{k=0..floor((n1)/2)} mod(binomial(nk1, k), 3).
%t Table[Sum[Mod[Binomial[n  k  1, k], 3], {k, 0, Floor[(n  1)/2]}], {n, 0, 100}] (* _G. C. Greubel_, Jan 17 2018 *)
%o (PARI) for(n=0,100, print1(sum(k=0,floor((n1)/2), lift(Mod(binomial(nk1,k),3))), ", ")) \\ _G. C. Greubel_, Jan 17 2018
%o (MAGMA) [0] cat [(&+[Binomial(nk1,k) mod 3: k in [0..Floor((n1)/2)]]): n in [1..100]]; // _G. C. Greubel_, Jan 17 2018
%Y Cf. A002487, A051638.
%K easy,nonn
%O 0,4
%A _Paul Barry_, Sep 13 2004
