This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A126837 #11 Jan 05 2025 01:10:51 %S A126837 1,25,7,47,28,28,14,4,37,14,22,35,21,7,0,31,28,43,0,42,0,11,46,28,32, %T A126837 35,28,21,23,0,0,31,7,14,0,24,46,0,0,14,14,0,37,5,7,23,42,21,0,16,0,7, %U A126837 36,14,28,7,0,36,42,0,14,0,28,7,0,28,15,42,28,0,2,1,14,23,28,0,14,0,39,35,46 %N A126837 Ramanujan numbers (A000594) read mod 7^2. %H A126837 Seiichi Manyama, <a href="/A126837/b126837.txt">Table of n, a(n) for n = 1..10000</a> %H A126837 Oddmund Kolberg, <a href="https://doi.org/10.7146/math.scand.a-10524">Note on Ramanujan's Function tau(n)</a>, Mathematica Scandinavica, Vol. 10 (1962), pp. 171-172; <a href="https://eudml.org/doc/165800">alternative link</a>. %H A126837 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 A126837 a(n) == n * sigma_9(n) (mod 7^2) if Legendre symbol (n,7) = A175629(n) = -1 (Kolberg, 1962). - _Amiram Eldar_, Jan 05 2025 %t A126837 a[n_] := Mod[RamanujanTau[n], 49]; Array[a, 100] (* _Amiram Eldar_, Jan 05 2025 *) %o A126837 (PARI) a(n) = ramanujantau(n) % 49; \\ _Amiram Eldar_, Jan 05 2025 %Y A126837 Cf. A000594, A013957, A126836 (mod 7^1), this sequence (mod 7^2), A126838 (mod 7^3). %K A126837 nonn %O A126837 1,2 %A A126837 _N. J. A. Sloane_, Feb 25 2007