A300118 - OEIS

A300118

Number of skew partitions whose quotient diagram is connected and whose numerator is the integer partition with Heinz number n.

1, 2, 3, 3, 4, 4, 5, 4, 6, 5, 6, 5, 7, 6, 7, 5, 8, 7, 9, 6, 8, 7, 10, 6, 10, 8, 10, 7, 11, 8, 12, 6, 9, 9, 11, 8, 13, 10, 10, 7, 14, 9, 15, 8, 11, 11, 16, 7, 15, 11, 11, 9, 17, 11, 12, 8, 12, 12, 18, 9, 19, 13, 12, 7, 13, 10, 20, 10, 13, 12, 21, 9, 22, 14, 15, 11

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OFFSET

1,2

COMMENTS

The diagram of a connected skew partition is required to be connected as a polyomino but can have empty rows or columns.

LINKS

Table of n, a(n) for n=1..76.

EXAMPLE

The a(15) = 7 denominators are (), (1), (11), (22), (3), (31), (32) with diagrams:

o o o . o o . o o . . o . . . . . . o o o

o o o o . o . . o o . o o o

Missing are the two disconnected skew partitions:

. . o . . o

o o . o

MATHEMATICA

primeMS[n_]:=If[n===1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];

undcon[y_]:=Select[Tuples[Range[0, #]&/@y], Function[v, GreaterEqual@@v&&With[{r=Select[Range[Length[y]], y[[#]]=!=v[[#]]&]}, Or[Length[r]<=1, And@@Table[v[[i]]<y[[i+1]], {i, Range[Min@@r, Max@@r-1]}]]]]];

Table[Length[undcon[Reverse[primeMS[n]]]], {n, 100}]

CROSSREFS

Cf. A000085, A000898, A056239, A006958, A138178, A153452, A238690, A259479, A259480, A296150, A297388, A299925, A299926, A300056, A300060, A300120, A300122, A300123, A300124.

Sequence in context: A227861 A336751 A294991 * A256544 A321211 A336515

Adjacent sequences: A300115 A300116 A300117 * A300119 A300120 A300121

KEYWORD

nonn

AUTHOR

Gus Wiseman, Feb 25 2018

STATUS

approved