A256344 - OEIS

%I #11 Mar 09 2021 20:15:17

%S 13,26,39,47,52,78,79,91,94,104,113,141,143,156,158,169,173,182,188,

%T 197,208,226,237,247,273,282,286,299,312,316,329,338,339,346,353,364,

%U 376,377,394,403,416,429,439,452,474,481,494,507,517,519,546,553,559,564,572,591,598

%N Moduli n for which A248218(n) = 4 (length of the terminating cycle of 0 under x -> x^2+1 modulo n).

%C If x is a member and y is a member of this sequence or A248219 or A256342, then LCM(x,y) is a member. - _Robert Israel_, Mar 09 2021

%H Robert Israel, <a href="/A256344/b256344.txt">Table of n, a(n) for n = 1..10000</a>

%e See A256342 or A256349.

%p filter:= proc(n) local x, k, R,p;

%p   x:= 0; R[0]:= 0;

%p   for k from 1 do

%p     x:= x^2+1 mod n;

%p     if assigned(R[x]) then return evalb(k-R[x] = 4)

%p     else R[x]:= k

%p     fi

%p   od;

%p end proc:

%p select(filter, [$1..1000]); # _Robert Israel_, Mar 09 2021

%o (PARI) for(i=1,600,A248218(i)==4&&print1(i","))

%Y Cf. A248218, A248219, A256342 - A256349, A003095, A247981.

%K nonn

%O 1,1

%A _M. F. Hasler_, Mar 25 2015