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A322365
Denominator of the sum of inverse products of parts in all partitions of n.
8
1, 1, 2, 6, 3, 10, 180, 1260, 560, 15120, 151200, 26400, 4989600, 4633200, 1528800, 851350500, 54486432000, 34306272000, 793945152000, 105594705216000, 1396755360000, 77534573760000, 243923769048960000, 23087434930560000, 67322960257512960000, 4371620795942400000
OFFSET
0,3
LINKS
MAPLE
b:= proc(n, i) option remember; `if`(n=0 or i=1, 1,
b(n, i-1) +b(n-i, min(i, n-i))/i)
end:
a:= n-> denom(b(n$2)):
seq(a(n), n=0..30);
MATHEMATICA
b[n_, i_] := b[n, i] = If[n==0 || i==1, 1, b[n, i-1]+b[n-i, Min[i, n-i]]/i];
a[n_] := Denominator[b[n, n]];
a /@ Range[0, 30] (* Jean-François Alcover, Apr 29 2020, after Alois P. Heinz *)
PROG
(PARI) a(n) = {my(s=0); forpart(p=n, s += 1/vecprod(Vec(p))); denominator(s); } \\ Michel Marcus, Apr 29 2020
CROSSREFS
See A322364 for more information.
Sequence in context: A130684 A295644 A079178 * A297553 A347558 A317490
KEYWORD
nonn,frac
AUTHOR
Alois P. Heinz, Dec 04 2018
STATUS
approved