|
|
A362981
|
|
Heinz numbers of integer partitions such that 2*(least part) >= greatest part.
|
|
3
|
|
|
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 16, 17, 18, 19, 21, 23, 24, 25, 27, 29, 31, 32, 35, 36, 37, 41, 43, 45, 47, 48, 49, 53, 54, 55, 59, 61, 63, 64, 65, 67, 71, 72, 73, 75, 77, 79, 81, 83, 89, 91, 96, 97, 101, 103, 105, 107, 108, 109, 113, 119, 121, 125
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
The Heinz number of a partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k). This gives a bijective correspondence between positive integers and integer partitions.
By conjugation, also Heinz numbers of partitions whose greatest part appears at a middle position, namely k/2, (k+1)/2, or (k+2)/2, where k is the number of parts. These partitions have ranks A362622.
|
|
LINKS
|
|
|
EXAMPLE
|
The terms together with their prime indices begin:
1: {} 16: {1,1,1,1} 36: {1,1,2,2}
2: {1} 17: {7} 37: {12}
3: {2} 18: {1,2,2} 41: {13}
4: {1,1} 19: {8} 43: {14}
5: {3} 21: {2,4} 45: {2,2,3}
6: {1,2} 23: {9} 47: {15}
7: {4} 24: {1,1,1,2} 48: {1,1,1,1,2}
8: {1,1,1} 25: {3,3} 49: {4,4}
9: {2,2} 27: {2,2,2} 53: {16}
11: {5} 29: {10} 54: {1,2,2,2}
12: {1,1,2} 31: {11} 55: {3,5}
13: {6} 32: {1,1,1,1,1} 59: {17}
15: {2,3} 35: {3,4} 61: {18}
|
|
MATHEMATICA
|
prix[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Select[Range[100], 2*Min@@prix[#]>=Max@@prix[#]&]
|
|
CROSSREFS
|
For prime factors instead of indices we have A081306.
Partitions of this type are counted by A237824.
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|