cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A381637 Number of multisets that can be obtained by taking the sum of each block of a multiset partition of the prime indices of n into blocks with distinct sums.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 3, 1, 3, 2, 2, 1, 3, 1, 2, 2, 3, 1, 4, 1, 3, 2, 2, 2, 4, 1, 2, 2, 4, 1, 5, 1, 3, 3, 2, 1, 4, 1, 3, 2, 3, 1, 5, 2, 5, 2, 2, 1, 5, 1, 2, 2, 4, 2, 5, 1, 3, 2, 4, 1, 5, 1, 2, 3, 3, 2, 5, 1, 5, 2, 2, 1, 6, 2, 2, 2
Offset: 1

Views

Author

Gus Wiseman, Mar 10 2025

Keywords

Comments

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.

Examples

			The prime indices of 84 are {1,1,2,4}, with 7 multiset partitions into blocks with distinct sums:
  {{1,1,2,4}}
  {{1},{1,2,4}}
  {{2},{1,1,4}}
  {{1,1},{2,4}}
  {{1,2},{1,4}}
  {{1},{2},{1,4}}
  {{1},{4},{1,2}}
with block-sums: {8}, {1,7}, {2,6}, {2,6}, {3,5}, {1,2,5}, {1,3,4}, of which 6 are distinct, so a(84) = 6.
		

Crossrefs

Allowing any block-sums gives A317141 (lower A300383), before sums A001055.
Before taking sums we had A321469.
For distinct blocks instead of distinct block-sums we have A381452.
If each block is a set we have A381634 (zeros A381806), before sums A381633.
For equal instead of distinct block-sums we have A381872, before sums A321455.
Other multiset partitions of prime indices:
- For multisets of constant multisets (A000688) see A381455 (upper), A381453 (lower).
- For set multipartitions (A050320) see A381078 (upper), A381454 (lower).
- For sets of constant multisets (A050361) see A381715.
- For sets of constant multisets with distinct sums (A381635) see A381716, A381636.
A003963 gives product of prime indices.
A055396 gives least prime index, greatest A061395.
A056239 adds up prime indices, row sums of A112798.
A265947 counts refinement-ordered pairs of integer partitions.

Programs

  • Mathematica
    prix[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[mset_]:=Union[Sort[Sort/@(#/.x_Integer:>mset[[x]])]&/@sps[Range[Length[mset]]]];
    Table[Length[Union[Sort[Total/@#]&/@Select[mps[prix[n]],UnsameQ@@Total/@#&]]],{n,100}]

A382460 Number of integer partitions of n that can be partitioned into sets with distinct sums in exactly one way.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 3, 4, 6, 5, 10, 10, 13, 15, 22, 20, 32, 32, 43, 49, 65, 64, 92, 96, 121, 140, 173, 192
Offset: 0

Views

Author

Gus Wiseman, Mar 29 2025

Keywords

Examples

			The partition y = (3,3,2,1,1,1) has 2 partitions into sets: {{1},{3},{1,2},{1,3}} and {{1},{1,3},{1,2,3}}, but only the latter has distinct sums, so y is counted under a(11)
The a(1) = 1 through a(10) = 10 partitions (A=10):
  1  2  3  4    5    6     7    8      9      A
           211  221  411   322  332    441    433
                311  2211  331  422    522    442
                           511  611    711    622
                                3311   42111  811
                                32111         3322
                                              4411
                                              32221
                                              43111
                                              52111
		

Crossrefs

Twice-partitions of this type are counted by A279785.
Multiset partitions of this type are counted by A381633.
Normal multiset partitions of this type are counted by A381718.
These partitions are ranked by A381870.
For no choices we have A381990, ranks A381806, see A382078, ranks A293243.
For at least one choice we have A381992, ranks A382075, see A382077, ranks A382200.
For distinct blocks instead of block-sums we have A382079, ranks A293511.
MM-numbers of these multiset partitions are A382201, see A302478.
For constant instead of strict blocks we have A382301, ranks A381991.
Set multipartitions: A089259, A116540, A270995, A296119, A318360.
A000041 counts integer partitions, strict A000009.
A265947 counts refinement-ordered pairs of integer partitions.

Programs

  • Mathematica
    hwt[n_]:=Total[Cases[FactorInteger[n],{p_,k_}:>PrimePi[p]*k]];
    ssfacs[n_]:=If[n<=1,{{}},Join@@Table[(Prepend[#,d]&) /@ Select[ssfacs[n/d],Min@@#>d&],{d,Select[Rest[Divisors[n]],SquareFreeQ]}]];
    Table[Length[Select[IntegerPartitions[n], Length[Select[ssfacs[Times@@Prime/@#],UnsameQ@@hwt/@#&]]==1&]],{n,0,15}]

A300862 Solution to 1 = Sum_y Product_{k in y} a(k) for each n > 0, where the sum is over all integer partitions of n with an odd number of parts.

Original entry on oeis.org

1, 1, 0, 0, -1, -1, 0, 1, 1, 0, -2, -3, -2, 2, 7, 6, -3, -15, -19, -2, 32, 54, 24, -64, -153, -123, 95, 389, 444, -43, -966, -1475, -516, 2066, 4414, 3092, -3874, -12480, -12936, 3847, 32445, 45494, 8950, -77282, -147663, -86313, 157456, 435623, 399041, -229616, -1211479, -1535700, -73132
Offset: 1

Views

Author

Gus Wiseman, Mar 13 2018

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_]:=a[n]=1-Sum[Times@@a/@y,{y,Select[IntegerPartitions[n],Length[#]>1&&OddQ[Length[#]]&]}];
    Array[a,40]

A319242 Heinz numbers of strict integer partitions of odd numbers. Squarefree numbers whose prime indices sum to an odd number.

Original entry on oeis.org

2, 5, 6, 11, 14, 15, 17, 23, 26, 31, 33, 35, 38, 41, 42, 47, 51, 58, 59, 65, 67, 69, 73, 74, 77, 78, 83, 86, 93, 95, 97, 103, 105, 106, 109, 110, 114, 119, 122, 123, 127, 137, 141, 142, 143, 145, 149, 157, 158, 161, 167, 170, 174, 177, 178, 179, 182, 185, 191
Offset: 1

Views

Author

Gus Wiseman, Sep 15 2018

Keywords

Comments

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

Examples

			105 is the Heinz number of (4,3,2), which is strict and has odd weight, so 105 belongs to the sequence.
The sequence of all odd-weight strict partitions begins: (1), (3), (2,1), (5), (4,1), (3,2), (7), (9), (6,1), (11), (5,2), (4,3), (8,1), (13), (4,2,1).
		

Crossrefs

Complement of the union of A319241 and A013929.

Programs

  • Mathematica
    Select[Range[100],And[SquareFreeQ[#],OddQ[Total[Cases[FactorInteger[#],{p_,k_}:>k*PrimePi[p]]]]]&]

A357979 Second MTF-transform of A000041. Replace prime(k) with prime(A357977(k)) in the prime factorization of n.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 31, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 59, 32, 33, 62, 35, 36, 37, 38, 39, 40, 127, 42, 79, 44, 45, 46, 47, 48, 49, 50, 93, 52, 53, 54, 55, 56, 57, 58, 211, 60, 61, 118, 63, 64, 65, 66
Offset: 1

Views

Author

Gus Wiseman, Oct 24 2022

Keywords

Comments

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798. We define the MTF-transform as applying a function horizontally along a number's prime indices; see the Mathematica program.

Examples

			We have:
- 51 = prime(2) * prime(7),
- A357977(2) = 2,
- A357977(7) = 11,
- a(51) = prime(2) * prime(11) = 93.
		

Crossrefs

Other multiplicative sequences: A003961, A357852, A064988, A064989, A357980.
Applying the transformation only once gives A357977, strict A357978.
For primes instead of partition numbers we have A357983.
A000040 lists the primes.
A056239 adds up prime indices, row-sums of A112798.

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    mtf[f_][n_]:=Product[If[f[i]==0,1,Prime[f[i]]],{i,primeMS[n]}];
    Array[mtf[mtf[PartitionsP]],100]

A381994 Number of integer partitions of n that cannot be partitioned into sets with equal sums.

Original entry on oeis.org

0, 0, 0, 0, 1, 3, 3, 9, 12, 17, 27, 43, 46, 82, 103, 133, 181, 258, 295
Offset: 0

Views

Author

Gus Wiseman, Mar 17 2025

Keywords

Examples

			For y = (3,3,1,1) we have {{1,3},{1,3}}, so y is not counted under a(8).
For y = (3,2,2,1), although we have {{1,3},{2,2}}, the block {2,2} is not a set, so y is counted under a(8).
The a(4) = 1 through a(8) = 12 partitions:
  (2,1,1)  (2,2,1)    (4,1,1)      (3,2,2)        (3,3,2)
           (3,1,1)    (3,1,1,1)    (3,3,1)        (4,2,2)
           (2,1,1,1)  (2,1,1,1,1)  (5,1,1)        (6,1,1)
                                   (2,2,2,1)      (3,2,2,1)
                                   (3,2,1,1)      (4,2,1,1)
                                   (4,1,1,1)      (5,1,1,1)
                                   (2,2,1,1,1)    (2,2,2,1,1)
                                   (3,1,1,1,1)    (3,2,1,1,1)
                                   (2,1,1,1,1,1)  (4,1,1,1,1)
                                                  (2,2,1,1,1,1)
                                                  (3,1,1,1,1,1)
                                                  (2,1,1,1,1,1,1)
		

Crossrefs

More on set multipartitions: A089259, A116540, A270995, A296119, A318360.
Twice-partitions of this type are counted by A279788.
Interchanging "constant" with "strict" gives A381717, see A381635, A381636, A381991.
Normal multiset partitions of this type are counted by A381718, see A279785.
These partitions are ranked by A381719, zeros of A382080.
For distinct instead of equal block-sums we have A381990, ranked by A381806.
For constant instead of strict blocks we have A381993.
A000041 counts integer partitions, strict A000009.
A050320 counts factorizations into squarefree numbers, see A381078, A381454.
A050326 counts factorizations into distinct squarefree numbers.
A265947 counts refinement-ordered pairs of integer partitions.
A381633 counts set systems with distinct sums, see A381634, A293243.

Programs

  • Mathematica
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]& /@ sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]& /@ sps[Range[Length[set]]]];
    Table[Length[Select[IntegerPartitions[n], Length[Select[mps[#], And@@UnsameQ@@@#&&SameQ@@Total/@#&]]==0&]],{n,0,10}]

A294079 Strict Moebius function of the multiorder of integer partitions indexed by Heinz numbers.

Original entry on oeis.org

0, 1, 1, 0, 1, -1, 1, 0, 0, -1, 1, 1, 1, -1, -1, 0, 1, 1, 1, 1, -1, -1, 1, -1, 0, -1, 0, 1, 1, 1, 1, 0, -1, -1, -1, -1, 1, -1, -1, -1, 1, 2, 1, 1, 1, -1, 1, 1, 0, 1, -1, 1, 1, -1, -1, -1, -1, -1, 1, -3, 1, -1, 1, 0, -1, 2, 1, 1, -1, 1, 1, 2, 1, -1, 1, 1, -1, 2, 1, 1, 0, -1, 1, -2, -1, -1, -1, -1, 1, -3, -1
Offset: 1

Views

Author

Gus Wiseman, Feb 07 2018

Keywords

Comments

By convention a(1) = 0.
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).

Crossrefs

Programs

  • Mathematica
    nn=120;
    ptns=Table[If[n===1,{},Join@@Cases[FactorInteger[n]//Reverse,{p_,k_}:>Table[PrimePi[p],{k}]]],{n,nn}];
    tris=Join@@Map[Tuples[IntegerPartitions/@#]&,ptns];
    qmu[y_]:=qmu[y]=If[Length[y]===1,1,-Sum[Times@@qmu/@t,{t,Select[tris,And[Length[#]>1,Sort[Join@@#,Greater]===y,UnsameQ@@#]&]}]];
    qmu/@ptns

Formula

mu(y) = Sum_{g(t)=y} (-1)^d(t), where the sum is over all strict trees (A273873) whose multiset of leaves is the integer partition y, and d(t) is the number of non-leaf nodes in t.

A317146 Moebius function in the ranked poset of factorizations of n into factors > 1, evaluated at the minimum (the prime factorization of n).

Original entry on oeis.org

0, 1, 1, -1, 1, -1, 1, 0, -1, -1, 1, 1, 1, -1, -1, 0, 1, 1, 1, 1, -1, -1, 1, -1, -1, -1, 0, 1, 1, 2, 1, 0, -1, -1, -1, -1, 1, -1, -1, -1, 1, 2, 1, 1, 1, -1, 1, 1, -1, 1, -1, 1, 1, -1, -1, -1, -1, -1, 1, -3, 1, -1, 1, 0, -1, 2, 1, 1, -1, 2, 1, 2, 1, -1, 1, 1
Offset: 1

Views

Author

Gus Wiseman, Jul 22 2018

Keywords

Comments

If x and y are factorizations of the same integer and it is possible to produce x by further factoring the factors of y, flattening, and sorting, then x <= y.

Examples

			The factorizations of 60 followed by their Moebius values are the following. The second column sums to 0, as required.
  (2*2*3*5) -> -3
   (2*2*15) ->  1
   (2*3*10) ->  2
    (2*5*6) ->  2
     (2*30) -> -1
    (3*4*5) ->  2
     (3*20) -> -1
     (4*15) -> -1
     (5*12) -> -1
     (6*10) -> -1
       (60) ->  1
		

Crossrefs

Formula

Product_{k>=2} 1/(1-a(n)/n^s) = 1+P(s), Re(s)>1, where P(s) is the prime zeta function. - Tian Vlasic, Jan 25 2024

A317176 Number of chains of factorizations of n into factors > 1, ordered by refinement, starting with the prime factorization of n and ending with the maximum factorization (n).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 6, 1, 3, 1, 3, 1, 1, 1, 11, 1, 1, 2, 3, 1, 4, 1, 18, 1, 1, 1, 15, 1, 1, 1, 11, 1, 4, 1, 3, 3, 1, 1, 49, 1, 3, 1, 3, 1, 11, 1, 11, 1, 1, 1, 21, 1, 1, 3, 74, 1, 4, 1, 3, 1, 4, 1, 78, 1, 1, 3, 3, 1, 4, 1, 49, 6, 1, 1
Offset: 1

Views

Author

Gus Wiseman, Jul 23 2018

Keywords

Comments

If x and y are factorizations of the same integer and it is possible to produce x by further factoring the factors of y, flattening, and sorting, then x <= y.

Examples

			The a(24) = 11 chains:
  (2*2*2*3) < (24)
  (2*2*2*3) < (2*12)  < (24)
  (2*2*2*3) < (3*8)   < (24)
  (2*2*2*3) < (4*6)   < (24)
  (2*2*2*3) < (2*2*6) < (24)
  (2*2*2*3) < (2*3*4) < (24)
  (2*2*2*3) < (2*2*6) < (2*12) < (24)
  (2*2*2*3) < (2*2*6) < (4*6)  < (24)
  (2*2*2*3) < (2*3*4) < (2*12) < (24)
  (2*2*2*3) < (2*3*4) < (3*8)  < (24)
  (2*2*2*3) < (2*3*4) < (4*6)  < (24)
		

Crossrefs

Formula

a(prime^n) = A213427(n).

A294080 Same-tree Moebius function of the multiorder of integer partitions indexed by Heinz numbers.

Original entry on oeis.org

0, 1, 1, -1, 1, 0, 1, -1, -1, 0, 1, 2, 1, 0, 0, -2, 1, 0, 1, 0, 0, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, -1, 0, 0, 0, 3, 1, 0, 0, 2, 1, 0, 1, 0, 0, 0, 1, -3, -1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 2, -1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, -2, 0, 1, -4, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 8
Offset: 1

Views

Author

Gus Wiseman, Feb 07 2018

Keywords

Comments

By convention a(1) = 0.
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).

Crossrefs

Programs

  • Mathematica
    nn=120;
    ptns=Table[If[n===1,{},Join@@Cases[FactorInteger[n]//Reverse,{p_,k_}:>Table[PrimePi[p],{k}]]],{n,nn}];
    tris=Join@@Map[Tuples[IntegerPartitions/@#]&,ptns];
    rmu[y_]:=rmu[y]=If[Length[y]===1,1,-Sum[Times@@rmu/@t,{t,Select[tris,And[Length[#]>1,Sort[Join@@#,Greater]===y,SameQ@@Total/@#]&]}]];
    rmu/@ptns
  • PARI
    A056239(n) = { my(f); if(1==n, 0, f=factor(n); sum(i=1, #f~, f[i,2] * primepi(f[i,1]))); }
    muifbalancedfactorization(v) = if(!#v, 1, my(pw=A056239(v[1]), m=-1); for(i=1,#v,if(A056239(v[i])!=pw,return(0), m *= A294080(v[i]))); (m));
    A294080aux(n, m, facs) = if(1==n, muifbalancedfactorization(Vec(facs)), my(s=0, newfacs); fordiv(n, d, if((d>1)&&(d<=m), newfacs = List(facs); listput(newfacs,d); s += A294080aux(n/d, m, newfacs))); (s));
    A294080(n) = if(1==n,0,if(isprime(n),1,A294080aux(n, n-1, List([]))));
    \\ A memoized implementation:
    map294080 = Map();
    A294080(n) = if(1==n,0,if(isprime(n),1,if(mapisdefined(map294080,n), mapget(map294080,n), my(v=A294080aux(n, n-1, List([]))); mapput(map294080,n,v); (v)))); \\ Antti Karttunen, Sep 22 2018

Formula

mu(y) = Sum_{g(t)=y} (-1)^d(t), where the sum is over all same-trees (A281145, A294019) whose multiset of leaves is the integer partition y, and d(t) is the number of non-leaf nodes in t.
Previous Showing 41-50 of 53 results. Next