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A284018 The smallest square referenced in A038109 (Divisible exactly by the square of a prime). 3
4, 9, 4, 9, 4, 25, 4, 4, 4, 9, 49, 25, 4, 4, 9, 4, 9, 25, 4, 4, 9, 4, 49, 9, 4, 4, 4, 9, 121, 4, 9, 4, 4, 9, 49, 4, 25, 9, 4, 4, 169, 9, 4, 25, 4, 4, 4, 9, 25, 4, 9, 4, 4, 9, 4, 9, 4, 121, 4, 49, 4, 4, 9, 4, 25, 4, 9, 4, 9, 289, 4, 49, 4, 9, 4, 9, 4, 4, 25, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = p^2 where p is the least prime whose exponent in the prime factorization of A038109(n) is exactly 2. - Robert Israel, Mar 28 2017

LINKS

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

EXAMPLE

A038109(3)=12, 12 = 2*2*3, so 12 is divisible by the square of 2 which is 4.

MAPLE

N:= 1000: # to use the members of A038109 <= N

P:= select(isprime, [$1..floor(sqrt(N))]):

S:= {}:

for p in P do

  Ks:= select(t -> t mod p <> 0, {$1..floor(N/p^2)});

  R:= map(`*`, Ks, p^2) minus S;

  for r in R do B[r]:= p^2 od:

  S:= S union R;

od:

A038109:= sort(convert(S, list)): seq(B[A038109[i]], i=1..nops(A038109)); # Robert Israel, Mar 28 2017

CROSSREFS

Cf. A038109, A284017, A013929, A283919.

Sequence in context: A141653 A071793 A010714 * A089090 A204919 A113484

Adjacent sequences:  A284015 A284016 A284017 * A284019 A284020 A284021

KEYWORD

nonn

AUTHOR

Robert Price, Mar 18 2017

EXTENSIONS

Corrected by Robert Israel, Mar 28 2017

STATUS

approved

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Last modified May 31 22:45 EDT 2020. Contains 334756 sequences. (Running on oeis4.)