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A047232 Smallest k > n where n is a 4th power modulo k.

%I A047232 #17 May 25 2019 14:14:10
%S A047232 1,2,7,6,6,10,10,9,14,11,15,14,22,17,22,21,17,19,21,27,22,25,26,29,29,
%T A047232 27,37,33,31,46,34,33,46,34,37,38,38,41,43,42,41,43,47,49,49,55,49,53,
%U A047232 52,53,62,59,54,58,57,57,61,59,61,62,66,65,67,74,66,67,75,77,76,73,74
%N A047232 Smallest k > n where n is a 4th power modulo k.
%C A047232 a(n) = n+1 for n+1 in A192453. - _Robert Israel_, May 24 2019
%H A047232 Robert Israel, <a href="/A047232/b047232.txt">Table of n, a(n) for n = 0..10000</a>
%p A047232 N:= 100: # for a(0)..a(N)
%p A047232 V:= Array(0..N):
%p A047232 count:= 1: V[0]:= 1:
%p A047232 for k from 2 while count < N+1 do
%p A047232   R:= select(t -> t <= N and V[t] = 0,{seq(x^4 mod k,x=1..k/2)});
%p A047232   V[convert(R,list)]:= k;
%p A047232   count:= count + nops(R);
%p A047232 od:
%p A047232 convert(V,list); # _Robert Israel_, May 24 2019
%o A047232 (PARI) a(n) = {my(k=n+1); while (!ispower(Mod(n,k), 4), k++); k;} \\ _Michel Marcus_, May 25 2019
%Y A047232 Cf. A192453.
%K A047232 easy,nonn
%O A047232 0,2
%A A047232 _Henry Bottomley_, Jun 08 2000