%I #15 Nov 27 2017 12:42:19
%S 1,0,0,0,2,0,0,0,1,0,0,0,2,0,0,0,2,0,0,0,0,0,0,0,3,0,0,0,2,0,0,0,0,0,
%T 0,0,2,0,0,0,2,0,0,0,2,0,0,0,1,0,0,0,2,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,
%U 0,0,0,0,2,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,2,0,0,0,2,0,0,0,0
%N Ramanujan numbers (A000594) read mod 4.
%H Antti Karttunen, <a href="/A126812/b126812.txt">Table of n, a(n) for n = 1..65537</a>
%H H. P. F. Swinnerton-Dyer, <a href="http://dx.doi.org/10.1007/978-3-540-37802-0_1">On l-adic representations and congruences for coefficients of modular forms</a>, pp. 1-55 of Modular Functions of One Variable III (Antwerp 1972), Lect. Notes Math., 350, 1973.
%t Mod[#, 4] & /@ RamanujanTau@ Range@ 105 (* _Michael De Vlieger_, Nov 26 2017 *)
%o (PARI) A126812(n) = (ramanujantau(n)%4); \\ _Antti Karttunen_, Nov 26 2017
%Y Cf. A000594, A008442, A098108, A126813, A126814.
%K nonn
%O 1,5
%A _N. J. A. Sloane_, Feb 25 2007