|
|
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
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
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:
|
|
MATHEMATICA
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|