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 A100346 Number of compositions of n into divisors of n. 19
 1, 2, 2, 6, 2, 25, 2, 56, 20, 129, 2, 1628, 2, 742, 450, 5272, 2, 45316, 2, 83344, 3321, 29967, 2, 5105722, 572, 200390, 26426, 5469759, 2, 154004511, 2, 47350056, 226020, 9262157, 51886, 15140335650, 2, 63346598, 2044895, 14700095926, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..2000 FORMULA Coefficient of x^n in expansion of 1/(1-Sum_{d divides n} x^d ). MAPLE with(numtheory): G:=proc(n) local DV: DV:=divisors(n): 1/(1-sum(x^DV[j], j=1..tau(n))) end: seq(coeff(series(G(n), x=0, 80), x^n), n=1..44); # Emeric Deutsch, Feb 16 2005 # second Maple program: a:= proc(n) option remember; local b, l;       l, b:= numtheory[divisors](n),       proc(m) option remember; `if`(m=0, 1,          add(`if`(j>m, 0, b(m-j)), j=l))       end; b(n)     end: seq(a(n), n=1..50);  # Alois P. Heinz, Mar 28 2017 MATHEMATICA a[n_] := SeriesCoefficient[1/(1-DivisorSum[n, x^#&]), {x, 0, n}]; Array[a, 50] (* Jean-François Alcover, Apr 06 2017 *) CROSSREFS Cf. A018818. Sequence in context: A130674 A284839 A286376 * A306387 A308692 A319352 Adjacent sequences:  A100343 A100344 A100345 * A100347 A100348 A100349 KEYWORD easy,nonn AUTHOR Vladeta Jovovic, Dec 29 2004 EXTENSIONS More terms from Emeric Deutsch, Feb 16 2005 STATUS approved

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Last modified July 26 16:44 EDT 2021. Contains 346294 sequences. (Running on oeis4.)