This site is supported by donations to The OEIS Foundation.

 Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS". Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A070415 a(n) = 7^n mod 31. 2
 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, 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, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS 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 LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 FORMULA From R. J. Mathar, Apr 20 2010: (Start) a(n) = a(n - 15). 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) MATHEMATICA PowerMod[7, Range[0, 90], 31] (* Harvey P. Dale, Jul 23 2011 *) PROG (Sage) [power_mod(7, n, 31) for n in xrange(0, 82)] # Zerinvary Lajos, Nov 27 2009 (PARI) a(n) = lift(Mod(7, 31)^n); \\ Altug Alkan, Mar 20 2016 (MAGMA) [Modexp(7, n, 31): n in [0..100]]; // Bruno Berselli, Mar 22 2016 CROSSREFS Sequence in context: A138491 A022511 A113613 * A034083 A185455 A103570 Adjacent sequences:  A070412 A070413 A070414 * A070416 A070417 A070418 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, May 12 2002 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.