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A369254
Numbers k that have an odd number of divisors that are at most sqrt(k).
1
1, 2, 3, 5, 7, 11, 12, 13, 16, 17, 18, 19, 20, 23, 28, 29, 31, 32, 36, 37, 41, 43, 44, 45, 47, 48, 50, 52, 53, 59, 61, 63, 67, 68, 71, 73, 75, 76, 79, 80, 81, 83, 89, 92, 97, 98, 99, 100, 101, 103, 107, 109, 112, 113, 116, 117, 124, 127, 131, 137, 139, 147, 148, 149, 151, 153, 157, 162, 163, 164, 167, 171, 172, 173
OFFSET
1,2
EXAMPLE
1 has just one divisor 1, which is <= sqrt(1), therefore 1 is included.
Of the two divisors of 2, [1, 2], only 1 is at most sqrt(2), therefore 2 is included.
Of the three divisors of 4, [1, 2, 4], the first two are <= sqrt(4), and as two is not an odd number, 4 is NOT included in this sequence.
PROG
(PARI) \\ See A369253.
CROSSREFS
Positions of odd terms in A038548.
Cf. A369253 (characteristic function).
Sequence in context: A230918 A001742 A307714 * A073085 A340657 A316793
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 24 2024
STATUS
approved