login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A299201 Number of twice-partitions whose composite is the integer partition with Heinz number n. 19
1, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 5, 1, 2, 2, 5, 1, 4, 1, 4, 2, 2, 1, 8, 2, 2, 3, 4, 1, 6, 1, 7, 2, 2, 2, 11, 1, 2, 2, 8, 1, 5, 1, 4, 4, 2, 1, 16, 2, 4, 2, 4, 1, 7, 2, 7, 2, 2, 1, 13, 1, 2, 5, 11, 2, 5, 1, 4, 2, 6, 1, 19, 1, 2, 4, 4, 2, 5, 1, 13, 5, 2, 1, 13, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).

LINKS

Table of n, a(n) for n=1..85.

EXAMPLE

The a(36) = 11 twice-partitions:

(2211),

(22)(11), (211)(2), (221)(1), (21)(21),

(2)(2)(11), (2)(11)(2), (11)(2)(2), (22)(1)(1), (21)(2)(1),

(2)(2)(1)(1).

MATHEMATICA

nn=100;

ptns=Table[If[n===1, {}, Join@@Cases[FactorInteger[n]//Reverse, {p_, k_}:>Table[PrimePi[p], {k}]]], {n, nn}];

tris=Join@@Map[Tuples[IntegerPartitions/@#]&, ptns];

Table[Length[Select[tris, Sort[Join@@#, Greater]===y&]], {y, ptns}]

CROSSREFS

Cf. A000041, A063834, A112798, A196545, A273873, A281145, A289501, A290261, A296150, A299200, A299202, A299203.

Sequence in context: A129138 A112970 A112971 * A050379 A153024 A066921

Adjacent sequences:  A299198 A299199 A299200 * A299202 A299203 A299204

KEYWORD

nonn

AUTHOR

Gus Wiseman, Feb 05 2018

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 22 10:25 EST 2020. Contains 331144 sequences. (Running on oeis4.)