A328592 -id:A328592 - cp's OEIS frontend

A384907 Number of permutations of {1..n} with all distinct lengths of maximal anti-runs (not increasing by 1).

1, 1, 1, 5, 17, 97, 587, 4291, 33109, 319967, 3106433, 35554459, 419889707, 5632467097, 77342295637, 1201240551077, 18804238105133, 328322081898745, 5832312989183807, 113154541564902427, 2229027473451951265, 47899977701182298255, 1037672943682453127645

Offset: 0

Gus Wiseman, Jun 21 2025

nonn

			The permutation (1,2,4,3,5,7,8,6,9) has maximal anti-runs ((1),(2,4,3,5,7),(8,6,9)), with lengths (1,5,3), so is counted under a(9).
The a(0) = 1 through a(4) = 17 permutations:
  ()  (1)  (2,1)  (1,3,2)  (1,2,4,3)
                  (2,1,3)  (1,3,2,4)
                  (2,3,1)  (1,4,2,3)
                  (3,1,2)  (1,4,3,2)
                  (3,2,1)  (2,1,3,4)
                           (2,1,4,3)
                           (2,3,1,4)
                           (2,4,1,3)
                           (2,4,3,1)
                           (3,1,4,2)
                           (3,2,1,4)
                           (3,2,4,1)
                           (3,4,2,1)
                           (4,1,3,2)
                           (4,2,1,3)
                           (4,3,1,2)
                           (4,3,2,1)

Christian Sievers, Table of n, a(n) for n = 0..449

For subsets instead of permutations we have A384177.
For strict partitions we have A384880, for runs A384178.
For partitions we have A384885, for runs A384884.
For runs instead of anti-runs we have A384891.
A010027 counts permutations by maximal anti-runs, for runs A123513.
A034839 counts subsets by number of maximal runs, for strict partitions A116674.
A098859 counts Wilf partitions (distinct multiplicities), complement A336866.
A384893 counts subsets by number of maximal anti-runs, for partitions A268193, A384905.
Cf. A000255, A044813, A072574, A242882, A325325, A328592, A329739, A351202, A356606, A384886, A384892.

Table[Length[Select[Permutations[Range[n]],UnsameQ@@Length/@Split[#,#2!=#1+1&]&]],{n,0,10}]

a(n)=if(n,my(b(n)=sum(i=0,n-1,(-1)^i*(n-i)!*binomial(n-1,i)), d=floor(sqrt(2*n)), p=polcoef(prod(i=1,n,1+x*y^i,1+O(y*y^n)*((1-x^(d+1))/(1-x))),n,y)); sum(i=1,d,b(n+1-i)*i!*polcoef(p,i)),1) \\ Christian Sievers, Jun 22 2025

a(n) = Sum_{k=1..n} ( T(n,k) * A000255(n-k) ) for n>=1, where T(n,k) is the number of compositions of n into k distinct parts (cf. A072574).

a(11) and beyond from Christian Sievers, Jun 22 2025

A328870 Numbers whose lengths of runs of 1's in their reversed binary expansion are not weakly increasing.

Original entry on oeis.org

11, 19, 22, 23, 35, 38, 39, 43, 44, 45, 46, 47, 55, 67, 70, 71, 75, 76, 77, 78, 79, 83, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 103, 107, 110, 111, 131, 134, 135, 139, 140, 141, 142, 143, 147, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 163, 166, 167

Offset: 1

Gus Wiseman, Nov 12 2019

nonn

			The sequence of terms together with their reversed binary expansions begins:
  11: (1101)
  19: (11001)
  22: (01101)
  23: (11101)
  35: (110001)
  38: (011001)
  39: (111001)
  43: (110101)
  44: (001101)
  45: (101101)
  46: (011101)
  47: (111101)
  55: (111011)
  67: (1100001)
  70: (0110001)
  71: (1110001)
  75: (1101001)
  76: (0011001)
  77: (1011001)
  78: (0111001)

Complement of A328869.
The version for prime indices is A112769.
The binary expansion of n has A069010(n) runs of 1's.
Cf. A000120, A003714, A014081, A164707, A245563, A304678, A328592.

Select[Range[100],!LessEqual@@Length/@Split[Join@@Position[Reverse[IntegerDigits[#,2]],1],#2==#1+1&]&]

A328869 Numbers whose lengths of runs of 1's in their reversed binary expansion are weakly increasing.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 20, 21, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36, 37, 40, 41, 42, 48, 49, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 68, 69, 72, 73, 74, 80, 81, 82, 84, 85, 96, 97, 98, 99

Offset: 1

Gus Wiseman, Nov 12 2019

nonn

			The sequence of terms together with their reversed binary expansions begins:
   1: (1)
   2: (01)
   3: (11)
   4: (001)
   5: (101)
   6: (011)
   7: (111)
   8: (0001)
   9: (1001)
  10: (0101)
  12: (0011)
  13: (1011)
  14: (0111)
  15: (1111)
  16: (00001)
  17: (10001)
  18: (01001)
  20: (00101)
  21: (10101)
  24: (00011)

Complement of A328870.
The version for prime indices is A304678.
The binary expansion of n has A069010(n) runs of 1's.
Cf. A000120, A003714, A014081, A112769, A164707, A245563, A328592.

Select[Range[100],LessEqual@@Length/@Split[Join@@Position[Reverse[IntegerDigits[#,2]],1],#2==#1+1&]&]

A385892 In the sequence of run lengths of binary indices of each positive integer (A245563), remove all duplicate rows after the first and take the last term of each remaining row.

Original entry on oeis.org

1, 2, 1, 3, 1, 2, 4, 1, 1, 2, 3, 5, 1, 1, 1, 2, 2, 3, 4, 6, 1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 7, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5, 6, 8, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5, 5, 6, 7

Offset: 1

Gus Wiseman, Jul 18 2025

nonn

A binary index of n is any position of a 1 in its reversed binary expansion. The binary indices of n are row n of A048793.

			The binary indices of 53 are {1,3,5,6}, with maximal runs ((1),(3),(5,6)), with lengths (1,1,2), which is the 16th row of A385817, so a(16) = 2.

In the following references, "before" is short for "before removing duplicate rows".
Positions of firsts appearances appear to be A000071.
Without the removals we have A090996.
For sum instead of last we have A200648, before A000120.
For length instead of last we have A200650+1, before A069010 = A037800+1.
Last term of row n of A385817 (ranks A385818, before A385889), first A083368.
A245563 gives run lengths of binary indices, see A245562, A246029, A328592.
A384877 gives anti-run lengths of binary indices, A385816.
Cf. A001629, A044813, A048793, A164707, A200649, A384878, A384890, A385886.

Last/@DeleteDuplicates[Table[Length/@Split[Join@@Position[Reverse[IntegerDigits[n,2]],1],#2==#1+1&],{n,100}]]

A385890 Positions of first appearances in A245563 = run lengths of binary indices.

Original entry on oeis.org

1, 2, 4, 6, 8, 12, 14, 16, 22, 24, 28, 30, 32, 44, 46, 48, 54, 56, 60, 62, 64, 86, 88, 92, 94, 96, 108, 110, 112, 118, 120, 124, 126, 128, 172, 174, 176, 182, 184, 188, 190, 192, 214, 216, 220, 222, 224, 236, 238, 240, 246, 248, 252, 254, 256, 342, 344, 348

Offset: 1

Gus Wiseman, Jul 18 2025

nonn

A binary index of n is any position of a 1 in its reversed binary expansion. The binary indices of n are row n of A048793.

These are positions of firsts appearances in A245563, ranks A385889, reverse A245562.
A384175 counts subsets with all distinct lengths of maximal runs, complement A384176.
A384877 lists anti-run lengths of binary indices, ranks A385816.
Cf. A000120, A023758, A048793, A069010, A200649, A243815, A246029, A328592, A384890.

bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
q=Table[Length/@Split[bpe[n],#2==#1+1&],{n,0,1000}];
Select[Range[Length[q]-1],!MemberQ[Take[q,#-1],q[[#]]]&]

cp's OEIS Frontend

A384907 Number of permutations of {1..n} with all distinct lengths of maximal anti-runs (not increasing by 1).

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A328870 Numbers whose lengths of runs of 1's in their reversed binary expansion are not weakly increasing.

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A328869 Numbers whose lengths of runs of 1's in their reversed binary expansion are weakly increasing.

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A385892 In the sequence of run lengths of binary indices of each positive integer (A245563), remove all duplicate rows after the first and take the last term of each remaining row.

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A385890 Positions of first appearances in A245563 = run lengths of binary indices.

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