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 313 results. Next

A089408 Number of fixed points in range [A014137(n-1)..A014138(n-1)] of permutation A089864.

Original entry on oeis.org

1, 1, 2, 1, 2, 2, 4, 5, 10, 14, 28, 42, 84, 132, 264, 429, 858, 1430, 2860, 4862, 9724, 16796, 33592, 58786, 117572, 208012, 416024, 742900, 1485800, 2674440, 5348880, 9694845, 19389690, 35357670, 70715340, 129644790, 259289580, 477638700
Offset: 0

Views

Author

Antti Karttunen, Nov 29 2003

Keywords

Comments

The number of n-node binary trees fixed by the corresponding automorphism(s). Essentially A000108 interleaved with A068875.

Crossrefs

Cf. A089402.
Cf. A000108.

Programs

  • Maple
    seq(seq(binomial(2*j,j)/(1+j)*i, i=1..2),j=0..19); # Zerinvary Lajos, Apr 29 2007
  • Mathematica
    a[0] = 1; a[n_] := If[EvenQ[n], 2*CatalanNumber[n/2 - 1], CatalanNumber[(n-1)/2]]; Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Jul 24 2013 *)
  • Python
    from sympy import catalan
    def a(n): return 1 if n==0 else 2*catalan(n//2 - 1) if n%2==0 else catalan((n - 1)//2) # Indranil Ghosh, May 23 2017
  • Scheme
    (define (A089408 n) (cond ((zero? n) 1) ((even? n) (* 2 (A000108 (-1+ (/ n 2))))) (else (A000108 (/ (-1+ n) 2)))))
    

Formula

a(0)=1, a(2n) = 2*A000108(n-1), a(2n+1) = A000108(n)
G.f.: (1+4x-(1+2x)sqrt(1-4x^2))/(2x). - Paul Barry, Apr 11 2005
a(2*j+i) = i*C(2*j,j)/(1+j), i=1..2, j >= 0. - Zerinvary Lajos, Apr 29 2007
D-finite with recurrence: (n+1)*a(n) - 2*a(n-1) + 4(3-n)*a(n-2) = 0. - R. J. Mathar, Dec 17 2011, corrected by Georg Fischer, Feb 13 2020

A057507 Number of cycles in range [A014137(n-1)..A014138(n-1)] of permutation A057505/A057506.

Original entry on oeis.org

1, 1, 1, 2, 3, 10, 18, 46, 95, 236, 528, 1288, 2936, 6984, 16212, 38528, 90717, 216648, 516358, 1240818, 2979992
Offset: 0

Views

Author

Antti Karttunen, Sep 03 2000

Keywords

Comments

For the convenience of the range notation above, we define A014137(-1) and A014138(-1) as zero.

Crossrefs

a(n) = A081148(n)+A081150(n). Bisections: A081151, A081167. Cf. A057545, A060114, A081164.
Occurs for first time in A073201 as row 2614.

A057545 Maximum cycle size in range [A014137(n-1)..A014138(n-1)] of permutation A057505/A057506.

Original entry on oeis.org

1, 1, 2, 3, 6, 6, 24, 72, 144, 147, 588, 672, 2136, 10152, 11520, 29484, 117936, 270576, 656352, 2062368, 4040160
Offset: 0

Views

Author

Antti Karttunen, Sep 07 2000

Keywords

Comments

For the convenience of the range notation above, we define A014137(-1) and A014138(-1) as zero.
Equal to the degree of the polynomials M_n(x) Donaghey gives on the page 81 of his paper.
Factored terms: 1, 1, 2, 3, 2*3, 2*3, 2^3 * 3, 2^3 * 3^2, 2^4 * 3^2, 3 * 7^2, 2^2 * 3 * 7^2, 2^5 * 3 * 7, 2^3 * 3 * 89, 2^3 * 3^3 * 47, 2^8 * 3^2 * 5, 2^2 * 3^4 * 7 * 13, 2^4 * 3^4 * 7 * 13, 2^4 * 3^2 * 1879, 2^5 * 3^2 * 43 * 53, 2^5 * 3^3 * 7 * 11 * 31, 2^5 * 3 * 5 * 19 * 443

Crossrefs

Occurs for first time in A073203 as row 2614.

A060114 Least common multiple of all cycle sizes in range [A014137(n-1)..A014138(n-1)] of permutation A057505/A057506.

Original entry on oeis.org

1, 1, 2, 6, 6, 30, 120, 720, 15120, 1164240, 15135120, 283931716867999200, 14510088480716327580681600, 3280681990411073806237542217555200, 936436634805345771521186435213604447980767985241556128000
Offset: 0

Views

Author

Antti Karttunen, Mar 01 2001

Keywords

Comments

For the convenience of the range notation above, we define A014137(-1) and A014138(-1) as zero.
This sequence grows so fast that it seems hopeless to count A057507 with Burnside's (orbit-counting) lemma.

Crossrefs

Occurs for first time in A073204 as row 2614.

A082852 a(0)=0, a(n) = A014137(A072643(n)-1).

Original entry on oeis.org

0, 1, 2, 2, 4, 4, 4, 4, 4, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65
Offset: 0

Views

Author

Antti Karttunen, Apr 17 2003

Keywords

Comments

A014137(n) occurs A000108(n+1) times.

Crossrefs

Used to compute A082853. Cf. also A082855.

Programs

  • Mathematica
    a014137[n_] := Sum[CatalanNumber[k], {k, 0, n}];
    a072643[n_] := Module[{i, c, a}, i = c = 0; a = 1; While[n > c, a *= (4*i + 2)/(i + 2); i++; c += a]; i];
    a[n_] := a014137[a072643[n] - 1];
    Table[a[n], {n, 0, 76}] (* Jean-François Alcover, Dec 26 2017 *)
  • Sage
    def A082852(n) :
        i = c = 0; a = 1
        while n > c :
            a *= (4*i+2)/(2+i)
            i += 1; c += a
        return c-a+1
    [A082852(n) for n in (0..76)] # - Peter Luschny, Sep 07 2012
  • Scheme
    (define (A082852 n) (if (zero? n) 0 (A014137 (-1+ (A072643 n)))))
    

A086586 Maximum cycle size in range [A014137(n-1)..A014138(n-1)] of permutations A074681/A074682 & A074683/A074684.

Original entry on oeis.org

1, 1, 2, 5, 9, 28, 57, 253, 842, 3753, 10927, 15014, 130831, 218961, 967104, 3767216, 29715310, 89923607, 314897868, 785059994
Offset: 0

Views

Author

Antti Karttunen, Jun 23 2003

Keywords

Comments

Shifted once right (beginning as 1,1,1,2,5,9,...) this is maximum cycle size (in the same range) of permutations A085169/A085170, shifted twice right (beginning as 1,1,1,1,2,5,9,...) this is the maximum cycle size in permutations A089867/A089868 and A089869/A089870.

A073191 Number of separate orbits/cycles to which the Catalan bijections A072796/A072797 partition each A000108(n) structures encoded in the range [A014137(n-1)..A014138(n-1)] of the sequence A014486/A063171.

Original entry on oeis.org

1, 1, 2, 4, 11, 31, 96, 305, 1007, 3389, 11636, 40498, 142714, 507870, 1823040, 6591885, 23989419, 87795473, 322922652, 1193058230, 4425547638, 16475756738, 61539293424, 230548633954, 866095934598, 3261868457698, 12313423931624
Offset: 0

Views

Author

Antti Karttunen, Jun 25 2002

Keywords

Crossrefs

Occurs for first time in A073201 as row 1.

Formula

a(n) = (A000108(n)+A073190(n))/2.

A073193 Number of separate orbits/cycles to which the Catalan bijection A057508 partitions each A000108(n) structures encoded in the range [A014137(n-1)..A014138(n-1)] of the sequence A014486/A063171.

Original entry on oeis.org

1, 1, 2, 4, 11, 30, 93, 292, 965, 3238, 11126, 38708, 136486, 485820, 1744677, 6310584, 22973793, 84103302, 309429066, 1143487428, 4242631626, 15798011604, 59018856522, 221143860936, 830895360978, 3129747395548, 11816242209260
Offset: 0

Views

Author

Antti Karttunen, Jun 25 2002

Keywords

Crossrefs

Occurs for first time in A073201 as row 168.

Formula

a(n) = (A000108(n)+A073192(n))/2

A073431 Number of separate orbits/cycles to which the Catalan bijections A069767/A069768 partition each A000108(n) structures encoded in the range [A014137(n-1)..A014138(n-1)] of the sequence A014486/A063171.

Original entry on oeis.org

1, 1, 1, 2, 3, 6, 12, 28, 65, 160, 408, 1074, 2898, 7998, 22508, 64426, 187251, 551730, 1645840, 4964876, 15130808, 46545788, 144424944, 451715460
Offset: 0

Views

Author

Antti Karttunen, Jul 31 2002

Keywords

Crossrefs

Occurs for first time in A073201 as row 6 (and 8). Column sums of the square array A074079/Row sums of the triangle A074080.

Programs

  • Maple
    A073431 := proc(n) local i; (1/2^n) * add((2^(n-i))*A073346bi(n,i),i=0..n); end;

Formula

a(0)=1, a(n) = (1/(2^(n-1))) * Sum_{i=1..(2^(n-1))} (Sum_{j=0..A007814(i)} A073346(n, j)) = (1/(2^(n-2))) * Sum_{i=1..(2^(n-1))} A073346(n, A007814(i)) - 1 = (1/2^n) * Sum_{i=0..n} (2^(n-i))*A073346(n, i) = Sum_{i=0..n} A074079(n, i)

A074080 Triangle T(n,k) (listed in order T(1,0), T(2,0), T(2,1), T(3,0), T(3,1), T(3,2), T(4,0), etc.) giving the number of 2^k-cycles that occur in the n-th sub-permutation of A069767/A069768 (i.e., in the range [A014137(n-1)..A014138(n-1)] inclusive).

Original entry on oeis.org

1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 2, 2, 1, 0, 0, 3, 5, 3, 1, 1, 0, 3, 10, 9, 4, 1, 0, 1, 3, 17, 24, 14, 5, 1, 0, 1, 3, 28, 57, 44, 20, 6, 1, 0, 0, 5, 41, 128, 128, 71, 27, 7, 1, 0, 1, 4, 60, 271, 354, 234, 106, 35, 8, 1, 0, 0, 5, 81, 549, 937, 738, 384, 150, 44, 9, 1, 0, 0, 5, 106, 1061
Offset: 0

Views

Author

Antti Karttunen, Aug 19 2002

Keywords

Examples

			If we take the fifth such sub-permutation, i.e., the subsequence A069767[23..64]: [45,46,48,49,50,54,55,57,58,59,61,62,63,64,44,47,53,56,60,43,52,40,31,32,41,34,35,36,42,51,39,30,33,38,29,26,27,37,28,25,24,23], subtract 22 from each term and convert the resulting permutation of [1..42] to disjoint cycle notation, we get:
(17,31),(20,21,30,29),(3,26,12,40),(6,32,8,35,7,33,11,39),(15,22,18,34,16,25,19,38),(1,23,9,36,4,27,13,41,2,24,10,37,5,28,14,42)
which implies that T(5,0) = 0 (no fixed elements), T(5,1) = 1 (one transposition), T(5,2) = 2 (two 4-cycles), T(5,3) = 2 (two 8-cycles), T(5,4) = 1 (and one 16-cycle). It is guaranteed that only cycles whose length is a power of 2 occur in A069767/A069768.
		

Crossrefs

Upper triangular region of the square array A074079 (actually, only the area above its main diagonal, excluding also the leftmost column). T(n, k) = A073430(n, k)/(2^k) [with the rightmost edge of A073430 discarded]. Row sums: A073431. A000108(n) = Sum_{i=0..n-1} 2^i * T(n, i). Cf. A073346, A003056, A002262.

Programs

Showing 1-10 of 313 results. Next