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 42 results. Next

A220656 The positions of those permutations in A030298 where the first element is not fixed.

Original entry on oeis.org

3, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100
Offset: 1

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Author

Antti Karttunen, Dec 17 2012

Keywords

Comments

Correspondingly, gives the positions of those terms in A030299 whose first digit is not 1, as long as the decimal encoding system employed is valid.

Crossrefs

Complement: A220696. Cf. A081291.

Programs

Formula

a(n) = A003422(1+A084558(n)) + A000142(A084558(n)) + A212598(n).
a(n) = A220655(n)+1.

A220696 The positions of those permutations in A030298 where the first element is one (fixed).

Original entry on oeis.org

1, 2, 4, 5, 10, 11, 12, 13, 14, 15, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179
Offset: 1

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Author

Antti Karttunen, Dec 17 2012

Keywords

Comments

Correspondingly gives the positions of those terms in A030299 whose first digit is 1, as long as the decimal encoding system employed is valid.

Crossrefs

Complement: A220656. Cf. A072795.

Formula

a(1)=1; and for n>1, a(n)=A220695(n-1)+1.

A030488 Position of n-th 1 in A030298.

Original entry on oeis.org

1, 2, 5, 6, 9, 13, 17, 19, 23, 24, 28, 32, 36, 40, 44, 49, 53, 58, 63, 66, 71, 73, 77, 82, 87, 90, 95, 97, 101, 106, 111, 114, 119, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220
Offset: 1

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Author

Keywords

A030489 Position of n-th 2 in A030298.

Original entry on oeis.org

3, 4, 7, 11, 12, 15, 20, 22, 25, 29, 34, 39, 42, 47, 48, 52, 56, 60, 64, 68, 74, 79, 81, 85, 91, 94, 98, 103, 105, 109, 115, 118, 121, 126, 131, 136, 141, 146, 152, 157, 163, 169, 173, 179, 182, 187, 193, 199, 203, 209, 212, 217, 223
Offset: 1

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Author

Keywords

A030490 Position of n-th 3 in A030298.

Original entry on oeis.org

8, 10, 14, 16, 18, 21, 26, 31, 33, 37, 43, 46, 50, 55, 57, 61, 67, 70, 72, 76, 80, 84, 88, 92, 99, 102, 107, 110, 113, 117, 122, 127, 133, 139, 143, 149, 151, 156, 161, 166, 171, 176, 183, 189, 192, 197, 204, 208, 213, 219, 222, 227
Offset: 1

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Author

Keywords

Crossrefs

Cf. A030298.

A030491 Position of n-th 4 in A030298.

Original entry on oeis.org

27, 30, 35, 38, 41, 45, 51, 54, 59, 62, 65, 69, 75, 78, 83, 86, 89, 93, 96, 100, 104, 108, 112, 116, 123, 129, 132, 137, 144, 148, 153, 159, 162, 167, 174, 178, 181, 186, 191, 196, 201, 206, 214, 218, 224, 228, 232, 237, 243, 249
Offset: 1

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Author

Keywords

A030492 Position of n-th 5 in A030298.

Original entry on oeis.org

124, 128, 134, 138, 142, 147, 154, 158, 164, 168, 172, 177, 184, 188, 194, 198, 202, 207, 211, 216, 221, 226, 231, 236, 244, 248, 254, 258, 262, 267, 274, 278, 284, 288, 292, 297, 304, 308, 314, 318, 322, 327, 331, 336, 341
Offset: 1

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Keywords

A030493 n-th partial sum of A030298.

Original entry on oeis.org

1, 2, 4, 6, 7, 8, 10, 13, 14, 17, 19, 21, 22, 25, 27, 30, 31, 34, 35, 37, 40, 42, 43, 44, 46, 49, 53, 54, 56, 60, 63, 64, 67, 69, 73, 74, 77, 81, 83, 84, 88, 90, 93, 94, 98, 101, 103, 105, 106, 109, 113, 115, 116, 120, 123, 125, 128, 129
Offset: 1

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Author

Keywords

A347208 Number of permutations of [n] that are in the same position in A030298 as they are in A098281.

Original entry on oeis.org

1, 2, 3, 3, 3, 10, 5, 4, 5, 13, 3, 6, 5
Offset: 1

Views

Author

William Chang, Aug 23 2021

Keywords

Examples

			For n = 7 the a(7) = 5 permutations are 1234567, 1234576, 1236745, 6574231, 7654321, which are in positions 1, 2, 17, 4198, 5040 respectively in both sequences A030298 and A098281.
		

Crossrefs

Programs

  • Mathematica
    perms[n_] := perms[n] = If[n == 1, {{1}}, Flatten[Table[Insert[#, n, pos], {pos, -1, -n, -1}]& /@ perms[n-1], 1]];
    a[n_] := Count[Transpose@{perms[n], Permutations[Range[n]]}, {p_, p_}];
    Table[a[n], {n, 1, 10}] (* Jean-François Alcover, Sep 02 2021 *)

A356324 a(n) is the first split point of the permutation p if p is the n-th permutation (in lexicographic order (A030298 prepended by the empty permutation)), or zero if it has no split point.

Original entry on oeis.org

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

Views

Author

Peter Luschny, Aug 03 2022

Keywords

Comments

A permutation p in [n] (where n >= 0) is reducible if there exist an i in 1..n-1 such that for all j in the range 1..i and all k in the range i+1..n it is true that p(j) < p(k). (Note that a range a..b includes a and b.) If such an i exists we say that i splits the permutation p at i and that i is a split point of p.
The list of permutations starts with the empty permutation (), which has no split points. The first permutation which has a split point is (1, 2).
The number of terms corresponding to the permutations of [n] which vanish is A003319(n), and the numbers of nonzero terms is A356291(n).

Examples

			Rows give the terms corresponding to the permutations of [n].
[0] [0]
[1] [0]
[2] [1, 0]
[3] [1, 1, 2, 0, 0, 0]
[4] [1, 1, 1, 1, 1, 1, 2, 2, 3, 0, 0, 0, 3, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0]
		

Crossrefs

Programs

  • SageMath
    def FirstSplit(p) -> int:
        n = p.size()
        for i in (1..n-1):
            ok = True
            for j in (1..i):
                if not ok: break
                for k in (i + 1..n):
                    if p(j) > p(k):
                        ok = False
                        break
            if ok: return i
        return 0
    def A356324_row(n): return [FirstSplit(p) for p in Permutations(n)]
    for n in range(6): print(A356324_row(n))
Showing 1-10 of 42 results. Next