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A171628 Number of compositions of n such that the smallest part is divisible by the number of parts. 1
1, 1, 1, 2, 3, 3, 3, 4, 6, 8, 11, 15, 19, 22, 25, 30, 37, 47, 62, 83, 108, 136, 168, 205, 247, 295, 354, 429, 524, 642, 789, 972, 1196, 1466, 1789, 2173, 2625, 3155, 3778, 4515, 5391, 6437, 7692, 9201, 11014, 13186, 15780, 18865, 22516, 26818, 31871, 37791 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..900

FORMULA

G.f.: Sum_{n>=0} [Sum_{d|n} x^(n*d)*(1-x^d)/(1-x)^d].

MAPLE

b:= proc(n, t, g) option remember; `if` (n=0, `if` (irem(g, t)=0, 1, 0), add (b(n-i, t+1, min(i, g)), i=1..n)) end: a:= n-> b(n, 0, infinity): seq (a(n), n=1..60); # Alois P. Heinz, Dec 15 2009

A171628 := proc(n) local g, k; g := 0 ; for k from 0 to n do g := g+add (x^(k*d)*(1-x^d)/(1-x)^d, d=numtheory[divisors](k)) ; g := expand(g) ; end do ; coeftayl(g, x=0, n) ; end proc: seq(A171628(n), n=1..60) ; # R. J. Mathar, Dec 14 2009

MATHEMATICA

b[n_, t_, g_] := b[n, t, g] = If[n == 0, If [Mod[g, t] == 0, 1, 0], Sum[b[n - i, t + 1, Min[i, g]], {i, n}]];

a[n_] := b[n, 0, Infinity];

Array[a, 60] (* Jean-Fran├žois Alcover, May 23 2020, after Alois P. Heinz *)

CROSSREFS

Cf. A168656, A171625.

Sequence in context: A327720 A327718 A035581 * A205566 A064338 A197592

Adjacent sequences:  A171625 A171626 A171627 * A171629 A171630 A171631

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Dec 13 2009

EXTENSIONS

More terms from R. J. Mathar and Alois P. Heinz, Dec 14 2009

STATUS

approved

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Last modified October 24 19:02 EDT 2020. Contains 338009 sequences. (Running on oeis4.)