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A276682
Number of divisors of the n-th 9-gonal number.
6
1, 3, 8, 4, 6, 4, 8, 12, 6, 6, 18, 8, 4, 8, 16, 8, 8, 9, 14, 24, 8, 4, 16, 12, 8, 8, 24, 8, 12, 12, 8, 20, 8, 4, 48, 24, 4, 12, 16, 24, 8, 12, 12, 16, 18, 4, 20, 16, 9, 16, 40, 8, 8, 8, 24, 36, 8, 4, 24, 24, 4, 16, 24, 12, 24, 8, 16, 16, 8, 12, 16, 18, 8, 16
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OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = A000005(A001106(n)).
EXAMPLE
a(2) = 3 because the 2nd 9-gonal number is 9, which has 3 divisors: 1,3,9.
MATHEMATICA
DivisorSigma[0, PolygonalNumber[9, Range[80]]] (* Harvey P. Dale, Dec 02 2024 *)
PROG
(PARI)
pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number
vector(150, n, numdiv(pg(9, n)))
CROSSREFS
Cf. A000005, A001106.
Cf. A063440 (m=3), A048691 (m=4), A276678 (m=5), A276679 (m=6), A276680 (m=7), A276681 (m=8), A276683 (m=10).
Sequence in context: A105722 A103559 A021030 * A303215 A240242 A340782
Adjacent sequences: A276679 A276680 A276681 * A276683 A276684 A276685
KEYWORD
nonn,changed
AUTHOR
Colin Barker, Sep 13 2016
STATUS
approved

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Last modified December 2 21:25 EST 2024. Contains 378341 sequences.
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