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 A113649 #21 Feb 16 2025 08:32:59 %S A113649 0,2,3,2,5,5,21,34,21,55,55,89,39,37,160,98,272,293,57,365,150,101, %T A113649 345,433,25,665,696,709,754,440,775,994,883,1090,765,1241,481,230, %U A113649 1511,1355,1599,257,1677,805,20,1382,752,289,2275,1525,1414,821,1484 %N A113649 Fibonacci(n-J(n,5)) mod n^2, where J is the Jacobi symbol. %C A113649 a(n) == 0 for n > 1 iff either n is a Wall-Sun-Sun prime (when n is prime) or a 'Wall-Sun-Sun pseudoprime' (when n is composite). The numbers meeting the second criterion are those composites where the congruence in A241505 is satisfied modulo n^2. No members are known from either of those two sets of numbers. - _Felix Fröhlich_, May 15 2015 %H A113649 T. D. Noe, <a href="/A113649/b113649.txt">Table of n, a(n) for n = 1..10000</a> %H A113649 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Wall-Sun-SunPrime.html">Wall-Sun-Sun Prime</a> %o A113649 (PARI) a(n)=lift(Mod([1, 1; 1, 0]^(n-kronecker(n, 5)), n^2)[1, 2]) \\ _Charles R Greathouse IV_, Oct 31 2011 %o A113649 (PARI) a(n) = fibonacci(n-kronecker(n,5)) % n^2 \\ _Jeppe Stig Nielsen_, Jul 22 2014 %o A113649 (Magma) [Fibonacci(n-(KroneckerSymbol(n,5))) mod n^2: n in [1..70]]; // _Vincenzo Librandi_, May 16 2015 %Y A113649 Cf. A113650. %K A113649 nonn %O A113649 1,2 %A A113649 _Eric W. Weisstein_, Nov 03 2005