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%I #18 Jan 05 2025 01:10:36
%S 1,4,0,5,0,0,0,4,2,0,1,0,0,0,0,3,0,1,0,0,0,4,4,0,4,0,0,0,2,0,0,3,0,0,
%T 0,3,4,0,0,0,0,0,2,5,0,2,0,0,0,2,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,
%U 0,0,2,1,0,2,0,0,0,0,4,0,4,0,0,0,0,1,0,4,0,0,0,6,0,0,0,0,0,0,2,6,0,0,0,0,0
%N Ramanujan numbers (A000594) read mod 7.
%H Seiichi Manyama, <a href="/A126836/b126836.txt">Table of n, a(n) for n = 1..10000</a>
%H R. P. Bambah, <a href="http://dx.doi.org/10.1090/S0002-9904-1947-08869-8">Ramanujan’s function tau(n)—A congruence property</a>, Bull. Amer. Math. Soc. 53 (1947), 764-765.
%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.
%F a(n) = n*sigma_3(n) mod 7. - _Michel Marcus_, Apr 25 2016
%t Mod[RamanujanTau@ #, 7] &@ Range@ 120 (* _Michael De Vlieger_, Apr 25 2016 *)
%o (PARI) a(n) = ramanujantau(n) % 7; \\ _Amiram Eldar_, Jan 05 2025
%Y Cf. A000594, A001158.
%Y Cf. this sequence (mod 7^1), A126837 (mod 7^2), A126838 (mod 7^3).
%K nonn,changed
%O 1,2
%A _N. J. A. Sloane_, Feb 25 2007