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A204919
a(n) = q^2 where q is the least prime such that n divides A204916(n)^2 - q^2.
2
4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 49, 4, 9, 4, 25, 289, 25, 4, 49, 4, 9, 4, 49, 4, 25, 4, 121, 9, 49, 961, 49, 4, 9, 4, 121, 4, 25, 4, 289, 1681, 25, 4, 361, 4, 49, 2209, 529, 4, 9, 4, 289, 4, 49
OFFSET
1,1
COMMENTS
For a guide to related sequences, see A204892.
Original name was "Least prime q^2 such that n divides p^2-q^2 for some prime p>q", which would be A089090. - Robert Israel, May 04 2019
LINKS
MAPLE
N:= 100: # to get a(1)..a(N)
A:= Vector(N): count:= 0:
p:= 2: P:= 2:
for i from 1 while count < N do
p:= nextprime(p);
ps:= p^2;
P:= P, p;
for j from 1 to i while count < N do
qs:= P[j]^2;
S:= convert(select(t -> t <= N and A[t]=0, numtheory:-divisors(ps-qs)), list);
A[S]:= qs;
count:= count + nops(S);
od od:
convert(A, list); # Robert Israel, May 04 2019
MATHEMATICA
(See the program at A204916.)
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jan 20 2012
EXTENSIONS
Name corrected by Robert Israel, May 04 2019
STATUS
approved