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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A325260 Number of integer partitions of n whose omega-sequence covers an initial interval of positive integers.

Original entry on oeis.org

1, 1, 2, 2, 4, 5, 5, 8, 10, 12, 13, 18, 19, 24, 25, 31, 33, 40, 40, 49, 51, 59, 60, 71, 72, 83, 84, 96, 98, 111, 111, 126, 128, 142, 143, 160, 161, 178, 179, 197, 199, 218, 218, 239, 241, 261, 262, 285, 286, 309, 310, 334, 336, 361, 361, 388, 390, 416, 417, 446
Offset: 0

Views

Author

Gus Wiseman, Apr 16 2019

Keywords

Comments

The omega-sequence of an integer partition is the sequence of lengths of the multisets obtained by repeatedly taking the multiset of multiplicities until a singleton is reached. For example, the partition (32211) has chain of multisets of multiplicities {1,1,2,2,3} -> {1,2,2} -> {1,2} -> {1,1} -> {2}, so its omega-sequence is (5,3,2,2,1).
The Heinz numbers of these partitions are given by A325251.

Examples

			The a(1) = 1 through a(9) = 12 partitions:
  (1)  (2)   (3)   (4)    (5)    (6)    (7)     (8)     (9)
       (11)  (21)  (22)   (32)   (33)   (43)    (44)    (54)
                   (31)   (41)   (42)   (52)    (53)    (63)
                   (211)  (221)  (51)   (61)    (62)    (72)
                          (311)  (411)  (322)   (71)    (81)
                                        (331)   (332)   (441)
                                        (511)   (422)   (522)
                                        (3211)  (611)   (711)
                                                (3221)  (3321)
                                                (4211)  (4221)
                                                        (4311)
                                                        (5211)
		

Crossrefs

Integer partition triangles: A008284 (first omega), A116608 (second omega), A325242 (third omega), A325268 (second-to-last omega), A225485 or A325280 (length/frequency depth).

Programs

  • Mathematica
    normQ[m_]:=Or[m=={},Union[m]==Range[Max[m]]];
    omseq[ptn_List]:=If[ptn=={},{},Length/@NestWhileList[Sort[Length/@Split[#]]&,ptn,Length[#]>1&]];
    Table[Length[Select[IntegerPartitions[n],normQ[omseq[#]]&]],{n,0,30}]

Formula

a(n) + A325262(n) = A000041(n).
Conjectures from Chai Wah Wu, Jan 13 2021: (Start)
a(n) = a(n-2) + a(n-3) + a(n-4) - a(n-5) - a(n-6) - a(n-7) + a(n-9) for n > 9.
G.f.: (-x^9 - x^8 - x^7 + x^6 - x^5 - x^2 - x - 1)/((x - 1)^3*(x + 1)^2*(x^2 + 1)*(x^2 + x + 1)). (End)

A325262 Number of integer partitions of n whose omega-sequence does not cover an initial interval of positive integers.

Original entry on oeis.org

0, 0, 0, 1, 1, 2, 6, 7, 12, 18, 29, 38, 58, 77, 110, 145, 198, 257, 345, 441, 576, 733, 942, 1184, 1503, 1875, 2352, 2914, 3620, 4454, 5493, 6716, 8221, 10001, 12167, 14723, 17816, 21459, 25836, 30988, 37139, 44365, 52956, 63022, 74934, 88873, 105296, 124469
Offset: 0

Views

Author

Gus Wiseman, Apr 23 2019

Keywords

Comments

The omega-sequence of an integer partition is the sequence of lengths of the multisets obtained by repeatedly taking the multiset of multiplicities until a singleton is reached. For example, the partition (32211) has chain of multisets of multiplicities {1,1,2,2,3} -> {1,2,2} -> {1,2} -> {1,1} -> {2}, so its omega-sequence is (5,3,2,2,1).

Examples

			The a(3) = 1 through a(9) = 18 partitions:
  (111)  (1111)  (2111)   (222)     (421)      (431)       (333)
                 (11111)  (321)     (2221)     (521)       (432)
                          (2211)    (4111)     (2222)      (531)
                          (3111)    (22111)    (3311)      (621)
                          (21111)   (31111)    (5111)      (3222)
                          (111111)  (211111)   (22211)     (6111)
                                    (1111111)  (32111)     (22221)
                                               (41111)     (32211)
                                               (221111)    (33111)
                                               (311111)    (42111)
                                               (2111111)   (51111)
                                               (11111111)  (222111)
                                                           (321111)
                                                           (411111)
                                                           (2211111)
                                                           (3111111)
                                                           (21111111)
                                                           (111111111)
		

Crossrefs

Integer partition triangles: A008284 (first omega), A116608 (second omega), A325242 (third omega), A325268 (second-to-last omega), A225485 or A325280 (frequency depth), A325249 (sum).

Programs

  • Mathematica
    normQ[m_]:=Or[m=={},Union[m]==Range[Max[m]]];
    omseq[ptn_List]:=If[ptn=={},{},Length/@NestWhileList[Sort[Length/@Split[#]]&,ptn,Length[#]>1&]];
    Table[Length[Select[IntegerPartitions[n],!normQ[omseq[#]]&]],{n,0,30}]

A325374 Numbers with adjusted frequency depth 3 whose prime indices cover an initial interval of positive integers.

Original entry on oeis.org

6, 30, 36, 210, 216, 900, 1296, 2310, 7776, 27000, 30030, 44100, 46656, 279936, 510510, 810000, 1679616, 5336100, 9261000, 9699690, 10077696, 24300000, 60466176, 223092870, 362797056, 729000000, 901800900, 1944810000, 2176782336, 6469693230, 12326391000
Offset: 1

Views

Author

Gus Wiseman, May 02 2019

Keywords

Comments

The adjusted frequency depth (A323014) of a positive integer n is 0 if n = 1, and otherwise it is 1 plus the number of times one must apply A181819 to reach a prime number, where A181819(k = p^i*...*q^j) = prime(i)*...*prime(j) = product of primes indexed by the prime exponents of k. For example, 180 has adjusted frequency depth 5 because we have: 180 -> 18 -> 6 -> 4 -> 3.
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k), so these are Heinz numbers of integer partitions with adjusted frequency depth 3 whose parts cover an initial interval of positive integers. The enumeration of these partitions by sum is given by A325334.
The terms are the primorial numbers (A002110) above 2 and all their powers. - Amiram Eldar, May 08 2019

Examples

			The sequence of terms together with their prime indices begins:
      6: {1,2}
     30: {1,2,3}
     36: {1,1,2,2}
    210: {1,2,3,4}
    216: {1,1,1,2,2,2}
    900: {1,1,2,2,3,3}
   1296: {1,1,1,1,2,2,2,2}
   2310: {1,2,3,4,5}
   7776: {1,1,1,1,1,2,2,2,2,2}
  27000: {1,1,1,2,2,2,3,3,3}
  30030: {1,2,3,4,5,6}
  44100: {1,1,2,2,3,3,4,4}
  46656: {1,1,1,1,1,1,2,2,2,2,2,2}
		

Crossrefs

Programs

  • Mathematica
    normQ[n_Integer]:=Or[n==1,PrimePi/@First/@FactorInteger[n]==Range[PrimeNu[n]]];
    fdadj[n_Integer]:=If[n==1,0,Length[NestWhileList[Times@@Prime/@Last/@FactorInteger[#1]&,n,!PrimeQ[#1]&]]];
    Select[Range[10000],normQ[#]&&fdadj[#]==3&]

A325413 Largest sum of the omega-sequence of an integer partition of n.

Original entry on oeis.org

0, 1, 3, 5, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70
Offset: 0

Views

Author

Gus Wiseman, Apr 24 2019

Keywords

Comments

The omega-sequence of an integer partition is the sequence of lengths of the multisets obtained by repeatedly taking the multiset of multiplicities until a singleton is reached. For example, the partition (32211) has chain of multisets of multiplicities {1,1,2,2,3} -> {1,2,2} -> {1,2} -> {1,1} -> {2}, so its omega-sequence is (5,3,2,2,1) with sum 13.
Appears to contain all nonnegative integers except 2, 4, 6, 7, and 11.

Examples

			The partitions of 9 organized by sum of omega-sequence (first column) are:
   1: (9)
   4: (333)
   5: (81) (72) (63) (54)
   7: (621) (531) (432)
   8: (711) (522) (441)
   9: (6111) (3222) (222111)
  10: (51111) (33111) (22221) (111111111)
  11: (411111)
  12: (5211) (4311) (4221) (3321) (3111111) (2211111)
  13: (42111) (32211) (21111111)
  14: (321111)
The largest term in the first column is 14, so a(9) = 14.
		

Crossrefs

Row lengths of A325414.
Integer partition triangles: A008284 (first omega), A116608 (second omega), A325242 (third omega), A325268 (second-to-last omega), A225485 or A325280 (frequency depth), A325414 (omega-sequence sum).

Programs

  • Mathematica
    omseq[ptn_List]:=If[ptn=={},{},Length/@NestWhileList[Sort[Length/@Split[#]]&,ptn,Length[#]>1&]];
    Table[Max[Total/@omseq/@IntegerPartitions[n]],{n,0,30}]

A325415 Number of distinct sums of omega-sequences of integer partitions of n.

Original entry on oeis.org

1, 1, 2, 3, 4, 5, 8, 8, 10, 11, 13, 12, 15, 14, 16, 18, 18, 18, 21, 20, 23, 23, 24, 24, 27, 27, 28, 29, 30, 30, 34, 32, 34, 35, 36, 37, 39, 38, 40, 41, 43, 42, 45, 44, 46, 48, 48, 48, 51, 50, 53, 53, 54, 54, 57, 57, 58, 59, 60, 60, 64
Offset: 0

Views

Author

Gus Wiseman, Apr 24 2019

Keywords

Comments

The omega-sequence of an integer partition is the sequence of lengths of the multisets obtained by repeatedly taking the multiset of multiplicities until a singleton is reached. For example, the partition (32211) has chain of multisets of multiplicities {1,1,2,2,3} -> {1,2,2} -> {1,2} -> {1,1} -> {2}, so its omega-sequence is (5,3,2,2,1) with sum 13.

Examples

			The partitions of 9 organized by sum of omega sequence (first column) are:
   1: (9)
   4: (333)
   5: (81) (72) (63) (54)
   7: (621) (531) (432)
   8: (711) (522) (441)
   9: (6111) (3222) (222111)
  10: (51111) (33111) (22221) (111111111)
  11: (411111)
  12: (5211) (4311) (4221) (3321) (3111111) (2211111)
  13: (42111) (32211) (21111111)
  14: (321111)
There are a total of 11 distinct sums {1,4,5,7,8,9,10,11,12,13,14}, so a(9) = 11.
		

Crossrefs

Number of nonzero terms in row n of A325414.
Integer partition triangles: A008284 (first omega), A116608 (second omega), A325242 (third omega), A325268 (second-to-last omega), A225485 or A325280 (frequency depth), A325414 (omega-sequence sum).

Programs

  • Mathematica
    omseq[ptn_List]:=If[ptn=={},{},Length/@NestWhileList[Sort[Length/@Split[#]]&,ptn,Length[#]>1&]];
    Table[Length[Union[Total/@omseq/@IntegerPartitions[n]]],{n,0,30}]

A325416 Least k such that the omega-sequence of k sums to n, and 0 if none exists.

Original entry on oeis.org

1, 2, 0, 4, 8, 6, 32, 30, 12, 24, 48, 96, 60, 120, 240, 480, 960, 1920, 3840, 2520, 5040, 10080, 20160, 40320, 80640
Offset: 0

Views

Author

Gus Wiseman, Apr 25 2019

Keywords

Comments

We define the omega-sequence of n (row n of A323023) to have length A323014(n) = adjusted frequency depth of n, and the k-th term is Omega(red^{k-1}(n)), where Omega = A001222 and red^{k} is the k-th functional iteration of red = A181819, defined by red(n = p^i*...*q^j) = prime(i)*...*prime(j) = product of primes indexed by the prime exponents of n. For example, we have 180 -> 18 -> 6 -> 4 -> 3, so the omega-sequence of 180 is (5,3,2,2,1) with sum 13.

Examples

			The sequence of terms together with their omega-sequences (n = 2 term not shown) begins:
     1:
     2:  1
     4:  2 1
     8:  3 1
     6:  2 2 1
    32:  5 1
    30:  3 3 1
    12:  3 2 2 1
    24:  4 2 2 1
    48:  5 2 2 1
    96:  6 2 2 1
    60:  4 3 2 2 1
   120:  5 3 2 2 1
   240:  6 3 2 2 1
   480:  7 3 2 2 1
   960:  8 3 2 2 1
  1920:  9 3 2 2 1
  3840: 10 3 2 2 1
  2520:  7 4 3 2 2 1
  5040:  8 4 3 2 2 1
		

Crossrefs

Omega-sequence statistics: A001222 (first omega), A001221 (second omega), A071625 (third omega), A323022 (fourth omega), A304465 (second-to-last omega), A182850 or A323014 (frequency depth), A325248 (Heinz number), A325249 (sum).

Programs

  • Mathematica
    omseq[n_Integer]:=If[n<=1,{},Total/@NestWhileList[Sort[Length/@Split[#]]&,Sort[Last/@FactorInteger[n]],Total[#]>1&]];
    da=Table[Total[omseq[n]],{n,10000}];
    Table[If[!MemberQ[da,k],0,Position[da,k][[1,1]]],{k,0,Max@@da}]

A325335 Number of integer partitions of n with adjusted frequency depth 4 whose parts cover an initial interval of positive integers.

Original entry on oeis.org

0, 0, 0, 0, 1, 2, 1, 3, 3, 3, 5, 8, 6, 13, 12, 14, 17, 22, 17, 28, 29, 30, 38, 50, 46, 67, 64, 75, 81, 104, 99, 127, 128, 150, 155, 201, 189, 236, 244, 293, 302, 363, 372, 437, 457, 548, 547, 638, 671, 754, 809, 922, 947, 1074, 1144, 1290, 1342, 1515, 1574
Offset: 0

Views

Author

Gus Wiseman, May 01 2019

Keywords

Comments

The adjusted frequency depth of an integer partition (A325280) is 0 if the partition is empty, and otherwise it is 1 plus the number of times one must take the multiset of multiplicities to reach a singleton. For example, the partition (32211) has adjusted frequency depth 5 because we have: (32211) -> (221) -> (21) -> (11) -> (2).
The Heinz numbers of these partitions are given by A325387.

Examples

			The a(4) = 1 through a(10) = 5 partitions:
  (211)  (221)   (21111)  (2221)    (22211)    (22221)     (222211)
         (2111)           (22111)   (221111)   (2211111)   (322111)
                          (211111)  (2111111)  (21111111)  (2221111)
                                                           (22111111)
                                                           (211111111)
		

Crossrefs

Programs

  • Mathematica
    normQ[m_]:=Or[m=={},Union[m]==Range[Max[m]]];
    fdadj[ptn_List]:=If[ptn=={},0,Length[NestWhileList[Sort[Length/@Split[#1]]&,ptn,Length[#1]>1&]]];
    Table[Length[Select[IntegerPartitions[n],normQ[#]&&fdadj[#]==4&]],{n,0,30}]

A325412 Number of distinct omega-sequences of integer partitions of n.

Original entry on oeis.org

1, 1, 2, 3, 5, 5, 10, 9, 14, 15, 20, 21, 33, 30, 39, 45, 54, 54, 69, 68, 85, 90, 100, 104, 128, 127, 141, 153, 172, 175, 205, 203, 229, 240, 257, 274, 308, 309, 335, 356, 390, 395, 437, 444, 481, 506, 530, 549, 602, 609, 648, 672, 710, 727, 777, 798, 848, 871
Offset: 0

Views

Author

Gus Wiseman, Apr 24 2019

Keywords

Comments

The omega-sequence of an integer partition is the sequence of lengths of the multisets obtained by repeatedly taking the multiset of multiplicities until a singleton is reached. For example, the partition (32211) has chain of multisets of multiplicities {1,1,2,2,3} -> {1,2,2} -> {1,2} -> {1,1} -> {2}, so its omega-sequence is (5,3,2,2,1).

Examples

			The a(1) = 1 through a(9) = 15 omega-sequences:
  (1)  (1)   (1)    (1)     (1)     (1)     (1)      (1)      (1)
       (21)  (31)   (21)    (51)    (21)    (71)     (21)     (31)
             (221)  (41)    (221)   (31)    (221)    (41)     (91)
                    (221)   (3221)  (61)    (331)    (81)     (221)
                    (3221)  (4221)  (221)   (3221)   (221)    (331)
                                    (331)   (4221)   (331)    (621)
                                    (421)   (5221)   (421)    (3221)
                                    (3221)  (6221)   (3221)   (4221)
                                    (4221)  (43221)  (4221)   (5221)
                                    (5221)           (5221)   (6221)
                                                     (6221)   (7221)
                                                     (7221)   (8221)
                                                     (43221)  (43221)
                                                     (53221)  (53221)
                                                              (63221)
		

Crossrefs

Integer partition triangles: A008284 (first omega), A116608 (second omega), A325242 (third omega), A325268 (second-to-last omega), A225485 or A325280 (frequency depth), A325414 (omega-sequence sum).

Programs

  • Mathematica
    omseq[ptn_List]:=If[ptn=={},{},Length/@NestWhileList[Sort[Length/@Split[#]]&,ptn,Length[#]>1&]];
    Table[Length[Union[omseq/@IntegerPartitions[n]]],{n,0,30}]

A325757 Irregular triangle read by rows giving the frequency span of n.

Original entry on oeis.org

1, 2, 1, 1, 2, 3, 1, 1, 1, 2, 2, 4, 1, 1, 1, 3, 2, 2, 2, 1, 1, 1, 2, 3, 5, 1, 1, 1, 1, 1, 2, 2, 2, 6, 1, 1, 1, 2, 4, 1, 1, 2, 2, 3, 1, 1, 1, 1, 4, 7, 1, 1, 1, 1, 2, 2, 2, 2, 8, 1, 1, 1, 1, 1, 2, 2, 3, 1, 1, 2, 2, 4, 1, 1, 1, 2, 5, 9, 1, 1, 1, 1, 1, 1, 2, 2, 3
Offset: 1

Views

Author

Gus Wiseman, May 19 2019

Keywords

Comments

We define the frequency span of an integer partition to be the partition itself if it has no or only one block, and otherwise it is the multiset union of the partition and the frequency span of its multiplicities. For example, the frequency span of (3,2,2,1) is {1,2,2,3} U {1,1,2} U {1,2} U {1,1} U {2} = {1,1,1,1,1,1,2,2,2,2,2,3}. The frequency span of a positive integer is the frequency span of its prime indices (row n of A296150).

Examples

			Triangle begins:
   1:
   2: 1
   3: 2
   4: 1 1 2
   5: 3
   6: 1 1 1 2 2
   7: 4
   8: 1 1 1 3
   9: 2 2 2
  10: 1 1 1 2 3
  11: 5
  12: 1 1 1 1 1 2 2 2
  13: 6
  14: 1 1 1 2 4
  15: 1 1 2 2 3
  16: 1 1 1 1 4
  17: 7
  18: 1 1 1 1 2 2 2 2
  19: 8
  20: 1 1 1 1 1 2 2 3
  21: 1 1 2 2 4
  22: 1 1 1 2 5
  23: 9
  24: 1 1 1 1 1 1 2 2 3
  25: 2 3 3
  26: 1 1 1 2 6
  27: 2 2 2 3
  28: 1 1 1 1 1 2 2 4
		

Crossrefs

Row lengths are A325249.
Run-lengths are A325758.
Number of distinct terms in row n is A325759(n).

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    freqspan[ptn_]:=If[Length[ptn]<=1,ptn,Sort[Join[ptn,freqspan[Sort[Length/@Split[ptn]]]]]];
    Table[freqspan[primeMS[n]],{n,15}]

A325758 Irregular triangle read by rows giving the frequency span signature of n.

Original entry on oeis.org

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

Views

Author

Gus Wiseman, May 19 2019

Keywords

Comments

We define the frequency span of an integer partition to be the partition itself if it has no or only one block, and otherwise it is the multiset union of the partition and the frequency span of its multiplicities. For example, the frequency span of (3,2,2,1) is {1,2,2,3} U {1,1,2} U {1,2} U {1,1} U {2} = {1,1,1,1,1,1,2,2,2,2,2,3}. The frequency span of a positive integer is the frequency span of its prime indices (row n of A296150). Row n of this triangle gives an unsorted list of the multiplicities in the frequency span of n. For example, the frequency span of 30 is {1,1,1,1,2,3,3}, so row 30 is (4,1,2).

Examples

			Triangle begins:
  1
  1
  2 1
  1
  3 2
  1
  3 1
  3
  3 1 1
  1
  5 3
  1
  3 1 1
  2 2 1
  4 1
  1
  4 4
  1
  5 2 1
  2 2 1
  3 1 1
  1
  6 2 1
  1 2
  3 1 1
  3 1
  5 2 1
  1
  4 1 2
		

Crossrefs

Row sums are A325249.
Row lengths are A325759.
Run-lengths of A325757.
Row n is the unsorted prime signature of A325760(n).

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    freqspan[ptn_]:=If[Length[ptn]<=1,ptn,Sort[Join[ptn,freqspan[Sort[Length/@Split[ptn]]]]]];
    Table[Length/@Split[freqspan[primeMS[n]]],{n,30}]
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