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A320048
One half of composite numbers k with the property that the symmetric representation of sigma(k) has two parts.
2
5, 7, 11, 13, 17, 19, 22, 23, 26, 29, 31, 34, 37, 38, 39, 41, 43, 46, 47, 51, 53, 57, 58, 59, 61, 62, 67, 68, 69, 71, 73, 74, 76, 79, 82, 83, 86, 87, 89, 92, 93, 94, 97, 101, 103, 106, 107, 109, 111, 113, 116, 118, 122, 123, 124, 127, 129, 131, 134, 137, 139, 141, 142, 146, 148, 149, 151, 157, 158, 159, 163, 164
OFFSET
1,1
COMMENTS
Also, even numbers of A239929 divided by two.
First differs from A101550 at a(51). - R. J. Mathar, Oct 04 2018
FORMULA
a(n) = A244894(n)/2.
EXAMPLE
5 is in the sequence because 10 is a composite number, and the symmetric representation of sigma(10) = 18 has two parts (as shown below), and 10/2 = 5.
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. _ _ _ _ _ _ 9
. |_ _ _ _ _ |
. | |_
. |_ _|_
. | |_ _ 9
. |_ _ |
. | |
. | |
. | |
. | |
. |_|
.
CROSSREFS
Cf. A101550, A237271 (number of parts), A237270, A237593, A238443, A238524, A239929 (two parts), A239660, A239929, A239932, A239934, A240062 (k parts), A244894, A245092, A262626, A280107 (four parts).
Sequence in context: A111906 A348471 A101550 * A246351 A272260 A322271
KEYWORD
nonn
AUTHOR
Omar E. Pol, Oct 04 2018
STATUS
approved