OFFSET
1,2
LINKS
R. P. Bambah and S. Chowla, A new congruence property of Ramanujan’s function tau(n), Bull. Amer. Math. Soc. 53 (1947), 768-769.
H. P. F. Swinnerton-Dyer, On l-adic representations and congruences for coefficients of modular forms, pp. 1-55 of Modular Functions of One Variable III (Antwerp 1972), Lect. Notes Math., 350, 1973.
FORMULA
a(n) = n^2*sigma(n) mod 9. - Michel Marcus, Apr 25 2016
MATHEMATICA
Mod[RamanujanTau@ #, 9] &@ Range@ 120 (* Michael De Vlieger, Apr 25 2016 *)
PROG
(PARI) a(n) = n^2*sigma(n) % 9; \\ Michel Marcus, Apr 26 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Feb 25 2007
STATUS
approved