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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 Colin Barker, Table of n, a(n) for n = 1..1000 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 Adjacent sequences: A276675 A276676 A276677 * A276679 A276680 A276681 KEYWORD nonn AUTHOR Colin Barker, Sep 13 2016 STATUS approved

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Last modified August 6 13:43 EDT 2024. Contains 374974 sequences. (Running on oeis4.)