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.

Showing 1-10 of 13 results. Next

A316313 Number of integer partitions of n such that every distinct submultiset has a different average.

Original entry on oeis.org

1, 1, 2, 2, 3, 3, 5, 6, 6, 9, 11, 10, 15, 17, 18, 22, 28, 26, 34, 37, 44, 50, 61, 53, 77, 82, 93, 89, 120, 120, 149, 138, 174, 180, 222, 193, 257, 262, 305, 281, 367, 359, 424, 398, 487, 507, 590, 526, 662, 666, 782, 729, 894, 892, 995, 987, 1154, 1188, 1370
Offset: 1

Views

Author

Gus Wiseman, Jun 29 2018

Keywords

Comments

Note that such a partition is necessarily strict.

Examples

			The a(8) = 6 integer partitions are (8), (71), (62), (53), (521), (431).
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[IntegerPartitions[n],UnsameQ@@Mean/@Union[Subsets[#]]&]],{n,20}]

A301899 Heinz numbers of strict knapsack partitions. Squarefree numbers such that every divisor has a different Heinz weight A056239(d).

Original entry on oeis.org

1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 46, 47, 51, 53, 55, 57, 58, 59, 61, 62, 65, 66, 67, 69, 71, 73, 74, 77, 78, 79, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 102, 103, 105, 106, 107, 109
Offset: 1

Views

Author

Gus Wiseman, Mar 28 2018

Keywords

Comments

An integer partition is knapsack if every distinct submultiset has a different sum. The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).

Examples

			42 is the Heinz number of (4,2,1) which is strict and knapsack, so is in the sequence. 45 is the Heinz number of (3,2,2) which is knapsack but not strict, so is not in the sequence. 30 is the Heinz number of (3,2,1) which is strict but not knapsack, so is not in the sequence.
Sequence of strict knapsack partitions begins: (), (1), (2), (3), (21), (4), (31), (5), (6), (41), (32), (7), (8), (42), (51), (9), (61).
		

Crossrefs

Programs

  • Mathematica
    wt[n_]:=If[n===1,0,Total[Cases[FactorInteger[n],{p_,k_}:>k*PrimePi[p]]]];
    Select[Range[100],SquareFreeQ[#]&&UnsameQ@@wt/@Divisors[#]&]

Formula

Intersection of A299702 and A005117.

A364532 Positive integers with a prime index equal to the sum of prime indices of some nonprime divisor. Heinz numbers of a variation of sum-full partitions.

Original entry on oeis.org

12, 24, 30, 36, 40, 48, 60, 63, 70, 72, 80, 84, 90, 96, 108, 112, 120, 126, 132, 140, 144, 150, 154, 156, 160, 165, 168, 180, 189, 192, 198, 200, 204, 210, 216, 220, 224, 228, 240, 252, 264, 270, 273, 276, 280, 286, 288, 300, 308, 312, 315, 320, 324, 325, 330
Offset: 1

Views

Author

Gus Wiseman, Aug 01 2023

Keywords

Comments

First differs from A299729 (non-knapsack) in lacking 525: {2,3,3,4}.
First differs from A325777 in having 462: {1,2,4,5} and lacking 675:{2,2,2,3,3}.
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.
These are the Heinz numbers of partitions containing the sum of some non-singleton submultiset.

Examples

			The terms together with their prime indices begin:
  12: {1,1,2}
  24: {1,1,1,2}
  30: {1,2,3}
  36: {1,1,2,2}
  40: {1,1,1,3}
  48: {1,1,1,1,2}
  60: {1,1,2,3}
  63: {2,2,4}
  70: {1,3,4}
  72: {1,1,1,2,2}
  80: {1,1,1,1,3}
  84: {1,1,2,4}
  90: {1,2,2,3}
  96: {1,1,1,1,1,2}
		

Crossrefs

Partitions not of this type are counted by A237667, strict A364349.
Partitions of this type are counted by A237668, strict A364272.
The binary complement is A364461, re-usable A364347 (counted by A364345).
The binary version is A364462, re-usable A364348 (counted by A363225).
The complement is A364531.
Subsets of this type are counted by A364534, complement A151897.
A000005 counts divisors, nonprime A033273, composite A055212.
A001222 counts prime indices.
A108917 counts knapsack partitions, strict A275972, for subsets A325864.
A112798 lists prime indices, sum A056239.
A299701 counts distinct subset-sums of prime indices.
A299702 ranks knapsack partitions, complement A299729.

Programs

  • Mathematica
    Select[Range[100],Intersection[prix[#],Total/@Subsets[prix[#],{2,Length[prix[#]]}]]!={}&]

A316402 Number of strict non-knapsack integer partitions of n, meaning not every subset has a different sum.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 1, 0, 3, 1, 4, 3, 8, 6, 12, 10, 20, 16, 29, 25, 44, 39, 61, 60, 91, 84, 125, 126, 180, 179, 242, 247, 336, 347, 444, 472, 606, 628, 796, 844, 1053, 1109, 1363, 1452, 1779, 1885, 2272, 2431, 2931, 3104, 3706, 3972, 4711, 5042, 5909, 6334
Offset: 1

Views

Author

Gus Wiseman, Jul 01 2018

Keywords

Examples

			The a(12) = 4 partitions are (6,4,2), (6,5,1), (5,4,2,1), (6,3,2,1).
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[IntegerPartitions[n],UnsameQ@@#&&!UnsameQ@@Total/@Union[Subsets[#]]&]],{n,30}]

Formula

a(n) = A000009(n) - A275972(n).

A316271 FDH numbers of strict non-knapsack partitions.

Original entry on oeis.org

24, 40, 70, 84, 120, 126, 135, 168, 198, 210, 216, 220, 231, 264, 270, 280, 286, 312, 330, 351, 360, 364, 378, 384, 408, 416, 420, 440, 456, 462, 504, 520, 528, 540, 544, 546, 552, 560, 576, 594, 600, 616, 630, 640, 646, 660, 663, 680, 696, 702, 728, 744, 748
Offset: 1

Views

Author

Gus Wiseman, Jun 28 2018

Keywords

Comments

A strict integer partition is knapsack if every subset has a different sum.
Let f(n) = A050376(n) be the n-th Fermi-Dirac prime. The FDH number of a strict integer partition (y_1,...,y_k) is f(y_1)*...*f(y_k).

Examples

			a(1) = 24 is the FDH number of (3,2,1), which is not knapsack because 3 = 2 + 1.
		

Crossrefs

Programs

  • Mathematica
    nn=1000;
    sksQ[ptn_]:=And[UnsameQ@@ptn,UnsameQ@@Plus@@@Union[Subsets[ptn]]];
    FDfactor[n_]:=If[n==1,{},Sort[Join@@Cases[FactorInteger[n],{p_,k_}:>Power[p,Cases[Position[IntegerDigits[k,2]//Reverse,1],{m_}->2^(m-1)]]]]];
    FDprimeList=Array[FDfactor,nn,1,Union];FDrules=MapIndexed[(#1->#2[[1]])&,FDprimeList];
    Select[Range[nn],!sksQ[FDfactor[#]/.FDrules]&]

A319319 Heinz numbers of integer partitions such that every distinct submultiset has a different GCD.

Original entry on oeis.org

1, 2, 3, 5, 7, 11, 13, 15, 17, 19, 23, 29, 31, 33, 35, 37, 41, 43, 47, 51, 53, 55, 59, 61, 67, 69, 71, 73, 77, 79, 83, 85, 89, 91, 93, 95, 97, 101, 103, 107, 109, 113, 119, 123, 127, 131, 137, 139, 141, 143, 145, 149, 151, 155, 157, 161, 163, 167, 173, 177
Offset: 1

Views

Author

Gus Wiseman, Sep 17 2018

Keywords

Comments

The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).
First differs from A304713 (Heinz numbers of pairwise indivisible partitions) at A304713(58) = 165, which is absent from this sequence because its prime indices are {2,3,5} and GCD(2,3) = GCD(2,3,5) = 1. The first term with more than two prime factors is 17719, which has prime indices {6,10,15}. The first term with more than two prime factors that is absent from A318716 is 296851, which has prime indices {12,20,30}.

Examples

			The sequence of partitions whose Heinz numbers are in the sequence begins: (), (1), (2), (3), (4), (5), (6), (3,2), (7), (8), (9), (10), (11), (5,2), (4,3), (12), (13), (14), (15), (7,2), (16), (5,3).
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n===1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    Select[Range[100],UnsameQ@@GCD@@@Union[Subsets[primeMS[#]]]&]

A316399 Number of strict integer partitions of n such that not every subset has a different average.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 0, 0, 2, 1, 1, 5, 3, 5, 9, 10, 10, 20, 20, 27, 32, 39, 43, 69, 65, 83, 99, 133, 136, 176, 191, 252, 274, 332, 363, 475, 503, 602, 677, 832, 893, 1067, 1186, 1418, 1561, 1797, 2000, 2384, 2602, 2992, 3315, 3853, 4226, 4826, 5383, 6121, 6763
Offset: 1

Views

Author

Gus Wiseman, Jul 01 2018

Keywords

Examples

			The a(12) = 5 partitions are (5,4,3), (6,4,2), (7,4,1), (5,4,2,1), (6,3,2,1).
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[IntegerPartitions[n],UnsameQ@@#&&!UnsameQ@@Mean/@Union[Subsets[#]]&]],{n,60}]

Formula

a(n) = A000009(n) - A316313(n).

A316400 Number of strict integer partitions of n that are knapsack (every subset has a different sum) but not every subset has a different average.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 0, 0, 4, 1, 2, 4, 6, 4, 13, 6, 13, 17, 15, 12, 31, 26, 27, 23, 36, 41, 56, 39, 47, 74, 71, 55, 101, 94, 110, 97, 145, 148, 189, 142, 214, 232, 280, 206, 362, 332, 414, 347, 504, 469, 658, 492, 726, 697, 867, 687, 1100, 933
Offset: 1

Views

Author

Gus Wiseman, Jul 01 2018

Keywords

Examples

			The a(21) = 13 partitions:
(8,7,6), (9,7,5), (10,7,4), (11,7,3), (12,7,2), (13,7,1),
(7,6,5,3), (8,6,4,3), (9,7,4,1), (10,6,3,2), (11,6,3,1), (12,4,3,2), (12,5,3,1).
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[IntegerPartitions[n],UnsameQ@@#&&UnsameQ@@Total/@Union[Subsets[#]]&&!UnsameQ@@Mean/@Union[Subsets[#]]&]],{n,20}]

A319327 Heinz numbers of integer partitions such that every distinct submultiset has a different LCM.

Original entry on oeis.org

1, 2, 3, 5, 7, 11, 13, 15, 17, 19, 23, 29, 31, 33, 35, 37, 41, 43, 47, 51, 53, 55, 59, 61, 67, 69, 71, 73, 77, 79, 83, 85, 89, 91, 93, 95, 97, 101, 103, 107, 109, 113, 119, 123, 127, 131, 137, 139, 141, 143, 145, 149, 151, 155, 157, 161, 163, 165, 167, 173
Offset: 1

Views

Author

Gus Wiseman, Sep 17 2018

Keywords

Comments

Note that such a Heinz number is necessarily squarefree, as such a partition is necessarily strict.
The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).
First differs from A304713 (Heinz numbers of pairwise indivisible partitions) at A304713(642) = 2093, which is absent from this sequence because its prime indices are {4,6,9} and LCM(4,9) = LCM(4,6,9) = 36.

Examples

			The sequence of partitions whose Heinz numbers are in the sequence begins: (), (1), (2), (3), (4), (5), (6), (3,2), (7), (8), (9), (10), (11), (5,2), (4,3), (12), (13), (14), (15), (7,2).
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n===1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    Select[Range[100],UnsameQ@@LCM@@@Union[Subsets[primeMS[#]]]&]

A319328 Heinz numbers of integer partitions such that not every distinct submultiset has a different GCD but every distinct submultiset has a different LCM.

Original entry on oeis.org

165, 255, 385, 465, 561, 595, 615, 759, 885, 935, 1001, 1005, 1015, 1023, 1045, 1085, 1173, 1245, 1309, 1353, 1435, 1455, 1505, 1547, 1581, 1615, 1635, 1705, 1771, 1905, 1947, 2065, 2091, 2139, 2211, 2235, 2255, 2345, 2355, 2365, 2387, 2397, 2409, 2431, 2465
Offset: 1

Views

Author

Gus Wiseman, Sep 17 2018

Keywords

Comments

The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).
The first term of this sequence absent from A302696 (numbers whose prime indices are pairwise coprime) is 1001 with prime indices {4,5,6}.

Examples

			The sequence of partitions whose Heinz numbers belong to this sequence begins (5,3,2), (7,3,2), (5,4,3), (11,3,2), (7,5,2), (7,4,3), (13,3,2), (9,5,2), (17,3,2), (7,5,3).
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    Select[Range[10000],UnsameQ@@primeMS[#]&&And[!UnsameQ@@GCD@@@Union[Rest[Subsets[primeMS[#]]]],UnsameQ@@LCM@@@Union[Rest[Subsets[primeMS[#]]]]]&]
Showing 1-10 of 13 results. Next