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 A276680 Number of divisors of the n-th heptagonal number. 6
 1, 2, 6, 4, 4, 5, 10, 6, 8, 4, 8, 12, 4, 4, 24, 16, 4, 8, 8, 8, 12, 4, 16, 24, 6, 4, 20, 8, 4, 18, 12, 10, 12, 4, 16, 16, 8, 8, 36, 12, 4, 16, 8, 16, 16, 4, 12, 24, 9, 12, 32, 8, 4, 10, 32, 12, 12, 8, 8, 40, 4, 4, 48, 12, 16, 12, 8, 8, 16, 8, 20, 48, 4, 4 (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(A000566(n)). EXAMPLE a(3) = 6 because the 3rd heptagonal number is 18, which has 6 divisors: 1,2,3,6,9,18. MATHEMATICA DivisorSigma[0, PolygonalNumber[7, Range[80]]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 09 2017 *) PROG (PARI) pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number vector(100, n, numdiv(pg(7, n))) CROSSREFS Cf. A000005, A000566. Cf. A063440 (m=3), A048691 (m=4), A276678 (m=5), A276679 (m=6), A276681 (m=8), A276682 (m=9), A276683 (m=10). Sequence in context: A160205 A187817 A276678 * A053794 A249913 A003077 Adjacent sequences: A276677 A276678 A276679 * A276681 A276682 A276683 KEYWORD nonn AUTHOR Colin Barker, Sep 13 2016 STATUS approved

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Last modified August 5 01:22 EDT 2024. Contains 374934 sequences. (Running on oeis4.)