A126828 Ramanujan numbers (A000594) read mod 81.

1, 57, 9, 67, 51, 27, 23, 78, 0, 72, 12, 36, 35, 15, 54, 70, 45, 0, 38, 15, 45, 36, 69, 54, 61, 51, 0, 2, 3, 0, 17, 9, 27, 54, 39, 0, 74, 60, 72, 9, 6, 54, 41, 75, 0, 45, 75, 63, 21, 75, 0, 77, 54, 0, 45, 12, 18, 9, 24, 54, 50, 78, 0, 37, 3, 0, 62, 18, 54, 36, 18, 0, 65, 6, 63, 35, 33, 54

Offset

1,2

Links

Table of n, a(n) for n=1..78.

R. P. Bambah and S. Chowla, Congruence properties of Ramanujan’s function tau(n), Bull. Amer. Math. Soc. 53 (1947), 950-955.

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+k)*sigma_7(n) with k=0 if gcd(n,3)=1 and k=9 if gcd(n,3)=2. - Michel Marcus, Apr 26 2016

Mathematica

Mod[RamanujanTau@ #, 81] & /@ Range@ 78 (* Michael De Vlieger, Apr 26 2016 *)

Crossrefs

Cf. A000594, A013955.

Sequence in context: A244190 A013682 A278068 * A241310 A355554 A033377

Adjacent sequences: A126825 A126826 A126827 * A126829 A126830 A126831

Keyword

nonn

Author

N. J. A. Sloane, Feb 25 2007

Status

approved