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A324333 Numbers d such that A324331(x)=d^2 only when x is a squarefree semiprime (A006881). 3
1, 2, 4, 6, 11, 12, 14, 16, 18, 20, 21, 22, 24, 25, 27, 29, 30, 32, 34, 35, 36, 38, 39, 41, 42, 43, 44, 45, 47, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 64, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 79, 81, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 97, 98, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Problem posed by Albert A. Mullin who asks if this sequence is infinite.

LINKS

Table of n, a(n) for n=1..70.

B. Alspach, Research problems, Problem 18, Discrete Math 40 (1982), page 126.

CROSSREFS

Cf. A000010, A000203, A006881.

Cf. A324331, A324334 (complement).

Sequence in context: A057661 A237277 A097954 * A081988 A244748 A245017

Adjacent sequences:  A324330 A324331 A324332 * A324334 A324335 A324336

KEYWORD

nonn

AUTHOR

Michel Marcus, Feb 23 2019

STATUS

approved

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Last modified September 25 09:26 EDT 2020. Contains 337335 sequences. (Running on oeis4.)