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 A070420 #31 Sep 08 2022 08:45:05 %S A070420 1,7,12,10,33,9,26,34,16,1,7,12,10,33,9,26,34,16,1,7,12,10,33,9,26,34, %T A070420 16,1,7,12,10,33,9,26,34,16,1,7,12,10,33,9,26,34,16,1,7,12,10,33,9,26, %U A070420 34,16,1,7,12,10,33,9,26,34,16,1,7,12,10,33,9,26,34,16,1,7,12,10,33,9 %N A070420 a(n) = 7^n mod 37. %C A070420 Sequence is periodic with length 9. Since a(18) = 1, 37 is composite in Z[sqrt(7)]: it can be factored as (10 - 3*sqrt(7))(10 + 3*sqrt(7)). - _Alonso del Arte_, Oct 12 2012 %H A070420 G. C. Greubel, <a href="/A070420/b070420.txt">Table of n, a(n) for n = 0..1000</a> %H A070420 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,1). %F A070420 From _R. J. Mathar_, Apr 20 2010: (Start) %F A070420 a(n) = a(n - 9). %F A070420 G.f.: ( -1 - 7*x - 12*x^2 - 10*x^3 - 33*x^4 - 9*x^5 - 26*x^6 - 34*x^7 - 16*x^8 ) / ( (x - 1)*(1 + x + x^2)*(x^6 + x^3 + 1) ). (End) %e A070420 a(2) = 12 because 7^2 = 49 and 49 - 37 = 12. %t A070420 PowerMod[7, Range[0, 74], 37] (* _Alonso del Arte_, Oct 12 2012 *) %o A070420 (Sage) [power_mod(7,n,37) for n in range(0,78)] # _Zerinvary Lajos_, Nov 27 2009 %o A070420 (PARI) a(n) = lift(Mod(7, 37)^n); \\ _Michel Marcus_, Mar 21 2016 %o A070420 (Magma) [Modexp(7, n, 37): n in [0..100]]; // _Bruno Berselli_, Mar 22 2016 %K A070420 nonn,easy %O A070420 0,2 %A A070420 _N. J. A. Sloane_, May 12 2002