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A276678 Number of divisors of the n-th pentagonal number. 6
1, 2, 6, 4, 4, 4, 8, 6, 6, 4, 10, 16, 4, 4, 16, 8, 6, 6, 12, 8, 8, 8, 8, 12, 6, 8, 32, 8, 4, 8, 8, 20, 12, 4, 24, 12, 8, 4, 16, 24, 4, 16, 14, 8, 12, 4, 16, 32, 6, 6, 24, 16, 4, 16, 16, 12, 16, 4, 16, 16, 8, 8, 24, 12, 8, 8, 18, 16, 8, 16, 8, 36, 4, 8, 60, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = A000005(A000326(n)). - Omar E. Pol, Sep 13 2016
EXAMPLE
a(7) = 8 because the 7th pentagonal number is 70, which has 8 divisors: 1,2,5,7,10,14,35,70.
PROG
(PARI)
pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number
vector(100, n, numdiv(pg(5, n)))
CROSSREFS
Cf. A000005, A000326 (pentagonal numbers).
Cf. A063440 (m=3), A048691 (m=4), A276679 (m=6), A276680 (m=7), A276681 (m=8), A276682 (m=9), A276683 (m=10).
Sequence in context: A029670 A160205 A187817 * A276680 A053794 A249913
KEYWORD
nonn
AUTHOR
Colin Barker, Sep 13 2016
STATUS
approved

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Last modified March 29 05:48 EDT 2024. Contains 371265 sequences. (Running on oeis4.)