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 1-7 of 7 results.

A035317 Pascal-like triangle associated with A000670.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 1, 3, 4, 2, 1, 4, 7, 6, 3, 1, 5, 11, 13, 9, 3, 1, 6, 16, 24, 22, 12, 4, 1, 7, 22, 40, 46, 34, 16, 4, 1, 8, 29, 62, 86, 80, 50, 20, 5, 1, 9, 37, 91, 148, 166, 130, 70, 25, 5, 1, 10, 46, 128, 239, 314, 296, 200, 95, 30, 6, 1, 11, 56, 174, 367, 553, 610, 496, 295, 125
Offset: 0

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Author

Keywords

Comments

From Johannes W. Meijer, Jul 20 2011: (Start)
The triangle sums, see A180662 for their definitions, link this "Races with Ties" triangle with several sequences, see the crossrefs. Observe that the Kn4 sums lead to the golden rectangle numbers A001654 and that the Fi1 and Fi2 sums lead to the Jacobsthal sequence A001045.
The series expansion of G(x, y) = 1/((y*x-1)*(y*x+1)*((y+1)*x-1)) as function of x leads to this sequence, see the second Maple program. (End)
T(2n,k) = the number of hatted frog arrangements with k frogs on the 2xn grid. See the linked paper "Frogs, hats and common subsequences". - Chris Cox, Apr 12 2024

Examples

			Triangle begins:
  1;
  1,  1;
  1,  2,  2;
  1,  3,  4,   2;
  1,  4,  7,   6,   3;
  1,  5, 11,  13,   9,   3;
  1,  6, 16,  24,  22,  12,   4;
  1,  7, 22,  40,  46,  34,  16,   4;
  1,  8, 29,  62,  86,  80,  50,  20,  5;
  1,  9, 37,  91, 148, 166, 130,  70, 25,  5;
  1, 10, 46, 128, 239, 314, 296, 200, 95, 30, 6;
  ...
		

Crossrefs

Row sums are A000975, diagonal sums are A080239.
Central terms are A014300.
Similar to the triangles A059259, A080242, A108561, A112555.
Cf. A059260.
Triangle sums (see the comments): A000975 (Row1), A059841 (Row2), A080239 (Kn11), A052952 (Kn21), A129696 (Kn22), A001906 (Kn3), A001654 (Kn4), A001045 (Fi1, Fi2), A023435 (Ca2), Gi2 (A193146), A190525 (Ze2), A193147 (Ze3), A181532 (Ze4). - Johannes W. Meijer, Jul 20 2011
Cf. A181971.

Programs

  • Haskell
    a035317 n k = a035317_tabl !! n !! k
    a035317_row n = a035317_tabl !! n
    a035317_tabl = map snd $ iterate f (0, [1]) where
       f (i, row) = (1 - i, zipWith (+) ([0] ++ row) (row ++ [i]))
    -- Reinhard Zumkeller, Jul 09 2012
    
  • Maple
    A035317 := proc(n,k): add((-1)^(i+k) * binomial(i+n-k+1, i), i=0..k) end: seq(seq(A035317(n,k), k=0..n), n=0..10); # Johannes W. Meijer, Jul 20 2011
    A035317 := proc(n,k): coeff(coeftayl(1/((y*x-1)*(y*x+1)*((y+1)*x-1)), x=0, n), y, k) end: seq(seq(A035317(n,k), k=0..n), n=0..10); # Johannes W. Meijer, Jul 20 2011
  • Mathematica
    t[n_, k_] := (-1)^k*(((-1)^k*(n+2)!*Hypergeometric2F1[1, n+3, k+2, -1])/((k+1)!*(n-k+1)!) + 2^(k-n-2)); Flatten[ Table[ t[n, k], {n, 0, 11}, {k, 0, n}]] (* Jean-François Alcover, Dec 14 2011, after Johannes W. Meijer *)
  • PARI
    {T(n,k)=if(n==k,(n+2)\2,if(k==0,1,if(n>k,T(n-1,k-1)+T(n-1,k))))}
    for(n=0,12,for(k=0,n,print1(T(n,k),","));print("")) \\ Paul D. Hanna, Jul 18 2012
    
  • Sage
    def A035317_row(n):
        @cached_function
        def prec(n, k):
            if k==n: return 1
            if k==0: return 0
            return -prec(n-1,k-1)-sum(prec(n,k+i-1) for i in (2..n-k+1))
        return [(-1)^k*prec(n+2, k) for k in (1..n)]
    for n in (1..11): print(A035317_row(n)) # Peter Luschny, Mar 16 2016

Formula

T(n,k) = Sum_{j=0..floor(n/2)} binomial(n-2j, k-2j). - Paul Barry, Feb 11 2003
From Johannes W. Meijer, Jul 20 2011: (Start)
T(n, k) = Sum_{i=0..k}((-1)^(i+k) * binomial(i+n-k+1,i)). (Mendelson)
T(n, k) = T(n-1, k-1) + T(n-1, k) with T(n, 0) = 1 and T(n, n) = floor(n/2) + 1. (Mendelson)
Sum_{k = 0..n}((-1)^k * (n-k+1)^n * T(n, k)) = A000670(n). (Mendelson)
T(n, n-k) = A128176(n, k); T(n+k, n-k) = A158909(n, k); T(2*n-k, k) = A092879(n, k). (End)
T(2*n+1,n) = A014301(n+1); T(2*n+1,n+1) = A026641(n+1). - Reinhard Zumkeller, Jul 19 2012

Extensions

More terms from James Sellers

A296327 T(n,k) = Number of n X k 0..1 arrays with each 1 horizontally, vertically or antidiagonally adjacent to 2 neighboring 1's.

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 5, 5, 1, 1, 8, 11, 8, 1, 1, 15, 23, 23, 15, 1, 1, 26, 54, 61, 54, 26, 1, 1, 45, 122, 185, 185, 122, 45, 1, 1, 80, 278, 562, 853, 562, 278, 80, 1, 1, 140, 634, 1677, 3569, 3569, 1677, 634, 140, 1, 1, 245, 1438, 4998, 14691, 20088, 14691, 4998, 1438, 245, 1, 1
Offset: 1

Views

Author

R. H. Hardin, Dec 10 2017

Keywords

Comments

Table starts
.1...1....1.....1......1.......1........1.........1...........1............1
.1...3....5.....8.....15......26.......45........80.........140..........245
.1...5...11....23.....54.....122......278.......634........1438.........3274
.1...8...23....61....185.....562.....1677......4998.......14968........44818
.1..15...54...185....853....3569....14691.....62193......261763......1099727
.1..26..122...562...3569...20088...112235....643541.....3666933.....20890748
.1..45..278..1677..14691..112235...850404...6660799....51754039....401363520
.1..80..634..4998..62193..643541..6660799..72224019...769931084...8196375877
.1.140.1438.14968.261763.3666933.51754039.769931084.11207386103.163095751500

Examples

			Some solutions for n=5, k=4
..1..1..0..0. .1..1..0..1. .0..0..0..0. .0..1..1..0. .0..1..0..0
..1..0..0..0. .1..0..1..1. .0..0..0..0. .0..1..0..0. .1..1..0..0
..0..0..0..0. .0..0..0..0. .0..0..1..1. .0..0..0..0. .0..0..0..0
..0..0..1..1. .0..0..1..0. .0..1..0..1. .0..0..0..1. .1..1..0..1
..0..0..1..0. .0..1..1..0. .0..1..1..0. .0..0..1..1. .1..0..1..1
		

Crossrefs

Column 2 is A193147(n+1).

Formula

Empirical for column k:
k=1: a(n) = a(n-1).
k=2: a(n) = a(n-1) +2*a(n-3) +a(n-5).
k=3: a(n) = 2*a(n-1) -a(n-2) +4*a(n-3) -2*a(n-4) +4*a(n-5) -3*a(n-6) +2*a(n-7) -a(n-8).
k=4: [order 14].
k=5: [order 40].
k=6: [order 83].

A296541 T(n,k)=Number of nXk 0..1 arrays with each 1 horizontally, vertically or antidiagonally adjacent to 2 or 4 neighboring 1s.

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 5, 5, 1, 1, 8, 16, 8, 1, 1, 15, 37, 37, 15, 1, 1, 26, 96, 126, 96, 26, 1, 1, 45, 254, 431, 431, 254, 45, 1, 1, 80, 654, 1554, 2104, 1554, 654, 80, 1, 1, 140, 1709, 5601, 10734, 10734, 5601, 1709, 140, 1, 1, 245, 4472, 20036, 53995, 78660, 53995, 20036
Offset: 1

Views

Author

R. H. Hardin, Dec 15 2017

Keywords

Comments

Table starts
.1...1....1.....1.......1........1.........1...........1............1
.1...3....5.....8......15.......26........45..........80..........140
.1...5...16....37......96......254.......654........1709.........4472
.1...8...37...126.....431.....1554......5601.......20036........71722
.1..15...96...431....2104....10734.....53995......270584......1360373
.1..26..254..1554...10734....78660....560942.....3987615.....28515358
.1..45..654..5601...53995...560942...5705431....57470370....581613058
.1..80.1709.20036..270584..3987615..57470370...820373528..11761387456
.1.140.4472.71722.1360373.28515358.581613058.11761387456.239372827502

Examples

			Some solutions for n=6 k=4
..0..1..0..0. .0..0..0..0. .1..1..0..0. .0..0..1..1. .0..0..0..0
..1..1..1..1. .0..0..0..0. .1..0..0..0. .0..1..0..1. .0..1..1..1
..0..1..1..0. .1..1..0..0. .0..0..0..0. .0..1..0..1. .0..1..1..0
..0..1..0..0. .1..0..0..1. .1..1..0..1. .0..1..1..0. .1..0..1..0
..1..1..1..0. .0..0..1..1. .1..0..1..1. .0..0..0..0. .1..0..1..0
..0..1..0..0. .0..0..0..0. .0..0..0..0. .0..0..0..0. .1..1..0..0
		

Crossrefs

Column 2 is A193147(n+1).

Formula

Empirical for column k:
k=1: a(n) = a(n-1)
k=2: a(n) = a(n-1) +2*a(n-3) +a(n-5)
k=3: [order 12]
k=4: [order 39]

A299595 T(n,k)=Number of nXk 0..1 arrays with every element unequal to 0, 1 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.

Original entry on oeis.org

1, 2, 2, 3, 1, 3, 5, 3, 3, 5, 8, 5, 5, 5, 8, 13, 8, 11, 11, 8, 13, 21, 15, 19, 23, 19, 15, 21, 34, 26, 35, 53, 53, 35, 26, 34, 55, 45, 65, 121, 113, 121, 65, 45, 55, 89, 80, 120, 250, 256, 256, 250, 120, 80, 89, 144, 140, 220, 533, 541, 576, 541, 533, 220, 140, 144, 233, 245
Offset: 1

Views

Author

R. H. Hardin, Feb 13 2018

Keywords

Comments

Table starts
..1..2...3....5....8...13....21....34....55.....89....144....233.....377
..2..1...3....5....8...15....26....45....80....140....245....431.....756
..3..3...5...11...19...35....65...120...220....404....744...1369....2517
..5..5..11...23...53..121...250...533..1162...2490...5327..11465...24641
..8..8..19...53..113..256...541..1148..2488...5349..11453..24617...52916
.13.15..35..121..256..576..1225..2601..5625..12100..25921..55696..119716
.21.26..65..250..541.1225..2583..5488.11899..25570..54750.117697..252985
.34.45.120..533.1148.2601..5488.11656.25269..54309.116285.249968..537305
.55.80.220.1162.2488.5625.11899.25269.54738.117679.252010.541648.1164265

Examples

			Some solutions for n=5 k=4
..0..0..1..0. .0..1..0..0. .0..1..0..0. .0..0..0..0. .0..0..0..0
..0..0..0..0. .0..0..0..0. .0..0..0..0. .0..0..0..1. .1..0..0..0
..0..0..0..0. .0..0..0..0. .0..0..0..1. .0..0..0..0. .0..0..0..0
..1..0..0..1. .1..0..0..0. .1..0..0..0. .1..0..0..0. .0..0..0..1
..0..0..0..0. .0..0..0..0. .0..0..0..0. .0..0..1..0. .0..0..0..0
		

Crossrefs

Column 1 is A000045(n+1).
Column 2 is A193147.

Formula

Empirical for diagonal: [linear recurrence of order 15] for n>18
Empirical for column k:
k=1: a(n) = a(n-1) +a(n-2)
k=2: a(n) = a(n-1) +2*a(n-3) +a(n-5) for n>6
k=3: a(n) = a(n-1) +2*a(n-3) +a(n-4) +a(n-5) for n>8
k=4..99: a(n) = a(n-1) +a(n-2) +3*a(n-3) +a(n-4) -a(n-5) -a(n-6) for n>9

A318545 T(n,k)=Number of nXk 0..1 arrays with every element unequal to 0, 1, 4 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.

Original entry on oeis.org

1, 2, 2, 3, 1, 3, 5, 3, 3, 5, 8, 5, 6, 5, 8, 13, 8, 13, 13, 8, 13, 21, 15, 26, 31, 26, 15, 21, 34, 26, 52, 78, 78, 52, 26, 34, 55, 45, 107, 207, 247, 207, 107, 45, 55, 89, 80, 218, 516, 784, 784, 516, 218, 80, 89, 144, 140, 442, 1288, 2349, 2905, 2349, 1288, 442, 140, 144, 233
Offset: 1

Views

Author

R. H. Hardin, Aug 28 2018

Keywords

Comments

Table starts
..1..2...3....5.....8.....13.....21......34.......55........89........144
..2..1...3....5.....8.....15.....26......45.......80.......140........245
..3..3...6...13....26.....52....107.....218......442.......899.......1829
..5..5..13...31....78....207....516....1288.....3270......8271......20866
..8..8..26...78...247....784...2349....7191....22268.....68384.....210050
.13.15..52..207...784...2905..10496...38721...144148....531780....1960675
.21.26.107..516..2349..10496..46165..208159...942764...4213744...18870716
.34.45.218.1288..7191..38721.208159.1143583..6263377..33963639..184912113
.55.80.442.3270.22268.144148.942764.6263377.41368803.271753441.1792754281

Examples

			Some solutions for n=5 k=4
..0..1..0..0. .0..0..0..0. .0..1..0..0. .0..0..0..0. .0..0..1..0
..0..0..0..1. .0..0..1..0. .0..0..0..0. .0..0..0..0. .0..0..0..0
..0..0..0..0. .0..0..0..0. .0..0..0..1. .1..0..0..0. .0..0..0..0
..0..0..0..0. .0..0..0..0. .1..0..0..0. .0..0..0..1. .1..0..0..1
..0..0..1..0. .0..1..0..0. .0..0..0..0. .0..0..0..0. .0..0..0..0
		

Crossrefs

Column 1 is A000045(n+1).
Column 2 is A193147.

Formula

Empirical for column k:
k=1: a(n) = a(n-1) +a(n-2)
k=2: a(n) = a(n-1) +2*a(n-3) +a(n-5) for n>6
k=3: a(n) = a(n-1) +3*a(n-3) +a(n-4) +3*a(n-5) +a(n-7) for n>8
k=4: [order 13] for n>14
k=5: [order 23] for n>24
k=6: [order 37] for n>38
k=7: [order 63] for n>64

A373717 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals, where T(n,k) = Sum_{j=0..floor(k*n/(2*k+1))} binomial(k * (n-2*j),j).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 4, 5, 4, 1, 1, 1, 1, 5, 7, 8, 6, 1, 1, 1, 1, 6, 9, 13, 15, 9, 1, 1, 1, 1, 7, 11, 19, 28, 26, 13, 1, 1, 1, 1, 8, 13, 26, 45, 53, 45, 19, 1, 1, 1, 1, 9, 15, 34, 66, 91, 105, 80, 28, 1, 1, 1, 1, 10, 17, 43, 91, 141, 201, 211, 140, 41, 1
Offset: 0

Views

Author

Seiichi Manyama, Jun 15 2024

Keywords

Examples

			Square array begins:
  1, 1,  1,  1,  1,  1,  1, ...
  1, 1,  1,  1,  1,  1,  1, ...
  1, 1,  1,  1,  1,  1,  1, ...
  1, 2,  3,  4,  5,  6,  7, ...
  1, 3,  5,  7,  9, 11, 13, ...
  1, 4,  8, 13, 19, 26, 34, ...
  1, 6, 15, 28, 45, 66, 91, ...
		

Crossrefs

Columns k=0..3 give A000012, A000930, A193147, A373718.
Main diagonal gives A373719.
Cf. A099233.

Programs

  • PARI
    T(n, k) = sum(j=0, k*n\(2*k+1), binomial(k*(n-2*j), j));

Formula

G.f. of column k: 1/(1 - x * (1 + x^2)^k).
T(n,k) = Sum_{j=0..k} binomial(k,j) * T(n-2*j-1,k).

A373706 Expansion of 1/(1 - x * (1 + x^4)^2).

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 5, 7, 9, 12, 19, 30, 45, 64, 91, 134, 201, 300, 440, 641, 939, 1386, 2050, 3021, 4437, 6516, 9588, 14128, 20811, 30624, 45042, 66268, 97545, 143604, 211368, 311040, 457704, 673605, 991437, 1459215, 2147563, 3160516, 4651330, 6845572, 10075042
Offset: 0

Views

Author

Seiichi Manyama, Jun 14 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, 2*n\9, binomial(2*n-8*k, k));

Formula

a(n) = a(n-1) + 2*a(n-5) + a(n-9) for n > 8.
a(n) = Sum_{k=0..floor(2*n/9)} binomial(2*n-8*k,k).
a(n) = A005711(2*n-1) for n > 0.
Showing 1-7 of 7 results.