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 A070415 #37 Dec 18 2023 14:10:02 %S A070415 1,7,18,2,14,5,4,28,10,8,25,20,16,19,9,1,7,18,2,14,5,4,28,10,8,25,20, %T A070415 16,19,9,1,7,18,2,14,5,4,28,10,8,25,20,16,19,9,1,7,18,2,14,5,4,28,10, %U A070415 8,25,20,16,19,9,1,7,18,2,14,5,4,28,10,8,25,20,16,19,9,1,7,18,2,14,5,4 %N A070415 a(n) = 7^n mod 31. %C A070415 Sequence is periodic with period length of 15. That a(15) = 1 means that 31 is not prime in Z[sqrt(7)], being factorable as (-1)*(9 - 4*sqrt(7))(9 + 4*sqrt(7)). - _Alonso del Arte_, Oct 11 2012 %H A070415 G. C. Greubel, <a href="/A070415/b070415.txt">Table of n, a(n) for n = 0..1000</a> %H A070415 <a href="/index/Rec#order_15">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1). %F A070415 From _R. J. Mathar_, Apr 20 2010: (Start) %F A070415 a(n) = a(n - 15). %F A070415 G.f.: ( -1 -7*x -18*x^2 -2*x^3 -14*x^4 -5*x^5 -4*x^6 -28*x^7 -10*x^8 -8*x^9 -25*x^10 -20*x^11 -16*x^12 -19*x^13 -9*x^14 ) / ( (x-1)*(1 +x^4 + x^3 +x^2 +x)*(1 +x +x^2)*(1 -x +x^3 -x^4 +x^5 -x^7 +x^8) ). (End) %t A070415 PowerMod[7, Range[0, 90], 31] (* _Harvey P. Dale_, Jul 23 2011 *) %o A070415 (Sage) [power_mod(7,n,31) for n in range(0,82)] # _Zerinvary Lajos_, Nov 27 2009 %o A070415 (PARI) a(n) = lift(Mod(7, 31)^n); \\ _Altug Alkan_, Mar 20 2016 %o A070415 (Magma) [Modexp(7, n, 31): n in [0..100]]; // _Bruno Berselli_, Mar 22 2016 %K A070415 nonn,easy %O A070415 0,2 %A A070415 _N. J. A. Sloane_, May 12 2002