%I #43 Mar 05 2022 14:12:29

%S 2,3,5,21,55,39,272,57,345,754,775,481,1599,1677,752,1484,590,2928,

%T 469,3905,4234,3871,1743,445,3589,9797,2266,2568,2834,6780,1651,8384,

%U 7946,16263,17880,9060,6908,26080,7348,22490,31146,23711,17954,5983

%N Fibonacci(p-J(p,5)) mod p^2, where p is the n-th prime and J is the Jacobi symbol.

%C A value of 0 indicates a Wall-Sun-Sun prime. No such prime is currently known. - _Felix Fröhlich_, Jun 07 2014

%H T. D. Noe, <a href="/A113650/b113650.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Wall-Sun-SunPrime.html">Wall-Sun-Sun Prime</a>

%t a[n_]:= ( p=Prime[n];Mod[Fibonacci[p-JacobiSymbol[p, 5]], Power[p, 2]]); Table[a[n], {n,1,50}] (* _Javier Rivera Romeu_, Mar 03 2022 *)

%o (PARI) a(n)=my(p=prime(n));lift(Mod([1,1;1,0]^(p-kronecker(p,5)),p^2)[1,2]) \\ _Charles R Greathouse IV_, Oct 31 2011

%o (Sage)

%o def a(n):

%o p = Primes().unrank(n-1)

%o return fibonacci(p-jacobi_symbol(p, 5))%pow(p, 2)

%o for n in range(1, 100): print(a(n), end=", ") # _Javier Rivera Romeu_, Mar 04 2022

%Y Cf. A113649.

%K nonn

%O 1,1

%A _Eric W. Weisstein_, Nov 03 2005