A204919 - OEIS

A204919

a(n) = q^2 where q is the least prime such that n divides A204916(n)^2 - q^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

Robert Israel, Table of n, a(n) for n = 1..10000

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

Cf. A089090, A204916, A204908, A204900, A204892.

Sequence in context: A010714 A284018 A089090 * A113484 A061767 A131016

Adjacent sequences: A204916 A204917 A204918 * A204920 A204921 A204922

KEYWORD

nonn

AUTHOR

Clark Kimberling, Jan 20 2012

EXTENSIONS

Name corrected by Robert Israel, May 04 2019

STATUS

approved