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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A212668 a(n) = (16/3)*(n+1)*n*(n-1) + 8*n^2 + 1.

Original entry on oeis.org

9, 65, 201, 449, 841, 1409, 2185, 3201, 4489, 6081, 8009, 10305, 13001, 16129, 19721, 23809, 28425, 33601, 39369, 45761, 52809, 60545, 69001, 78209, 88201, 99009, 110665, 123201, 136649, 151041, 166409, 182785, 200201, 218689, 238281, 259009, 280905, 304001
Offset: 1

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Author

Keywords

Comments

a(n) is the difference between numbers of nonnegative multiples of 2*n+1 with even and odd digit sum in base 2*n in interval [0, 32*n^5).

Crossrefs

Programs

  • Magma
    [(16/3)*(n+1)*n*(n-1)+8*n^2+1: n in [1..40]]; // Vincenzo Librandi, Dec 01 2015
  • Mathematica
    LinearRecurrence[{4, -6, 4, -1}, {9, 65, 201, 449}, 40] (* Vincenzo Librandi, Dec 01 2015 *)
    CoefficientList[Series[x (9+29x-5x^2-x^3)/(1-x)^4,{x,0,40}],x] (* Harvey P. Dale, Mar 29 2023 *)
  • PARI
    a(n)=16*(n+1)*n*(n-1)/3+8*n^2+1 \\ Charles R Greathouse IV, Oct 07 2015
    
  • PARI
    Vec(x*(9+29*x-5*x^2-x^3)/(1-x)^4 + O(x^100)) \\ Colin Barker, Nov 30 2015
    

Formula

a(n) = 2/(2*n+1)*Sum_{i=1..n} tan^5(Pi*i/(2*n+1)) * sin(2*Pi*i/(2*n+1)).
G.f.: x*(9+29*x-5*x^2-x^3) / (1-x)^4. - Colin Barker, Nov 30 2015

A064043 Number of length 3 walks on an n-dimensional hypercubic lattice starting at the origin and staying in the nonnegative part.

Original entry on oeis.org

0, 3, 18, 51, 108, 195, 318, 483, 696, 963, 1290, 1683, 2148, 2691, 3318, 4035, 4848, 5763, 6786, 7923, 9180, 10563, 12078, 13731, 15528, 17475, 19578, 21843, 24276, 26883, 29670, 32643, 35808, 39171, 42738, 46515, 50508, 54723, 59166, 63843, 68760, 73923, 79338
Offset: 0

Views

Author

Henry Bottomley, Aug 23 2001

Keywords

Crossrefs

Number of walks length 0, 1 and 2 are A000012, A001477 and A002378.
Cf. A084990.

Programs

  • Maple
    seq(sum(3*n+n^2-1, k=1..n), n=0..39); # Zerinvary Lajos, Jan 28 2008
  • Mathematica
    Table[n*(n^2 + 3n -1), {n,0,50}] (* G. C. Greubel, Jul 20 2017 *)
  • PARI
    a(n) = { n*(n^2 + 3*n - 1) } \\ Harry J. Smith, Sep 06 2009

Formula

a(n) = n*(n^2 + 3*n - 1) = n*A014209(n) = A064044(n, 3).
a(n) = a(n-1) + 3*A002378(n-1) + 6*A001477(n-1) + 3*A000012(n-1).
G.f.: 3*x*(1+2*x-x^2)/(1-x)^4. - Colin Barker, Apr 19 2012
E.g.f.: (x^3 + 6*x^2 + 3*x)*exp(x). - G. C. Greubel, Jul 20 2017
a(n) = A084990(n)/3. - Alois P. Heinz, Jul 21 2017

A212669 a(n) = 2/15 * (32*n^5 + 80*n^4 + 40*n^3 - 20*n^2 + 3*n).

Original entry on oeis.org

18, 340, 2022, 7400, 20602, 48060, 99022, 186064, 325602, 538404, 850102, 1291704, 1900106, 2718604, 3797406, 5194144, 6974386, 9212148, 11990406, 15401608, 19548186, 24543068, 30510190, 37585008, 45915010, 55660228, 66993750, 80102232, 95186410, 112461612
Offset: 1

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Author

Keywords

Comments

a(n) is the difference between numbers of nonnegative multiples of 2*n+1 with even and odd digit sum in base 2*n in interval [0, 64*n^6).

Crossrefs

Programs

  • PARI
    Vec(2*x*(9+116*x+126*x^2+4*x^3+x^4)/(1-x)^6 + O(x^50)) \\ Colin Barker, Dec 01 2015

Formula

a(n) = 2/(2*n+1)*Sum_{i=1..n} tan^6(Pi*i/(2*n+1)).
G.f.: 2*x*(9+116*x+126*x^2+4*x^3+x^4) / (1-x)^6. - Colin Barker, Dec 01 2015

A212670 a(n) = 1/15*(128*n^5 + 320*n^4 + 80*n^3 - 200*n^2 + 92*n - 15).

Original entry on oeis.org

27, 615, 3843, 14351, 40363, 94711, 195859, 368927, 646715, 1070727, 1692195, 2573103, 3787211, 5421079, 7575091, 10364479, 13920347, 18390695, 23941443, 30757455, 39043563, 49025591, 60951379, 75091807, 91741819, 111221447, 133876835, 160081263, 190236171
Offset: 1

Views

Author

Keywords

Comments

a(n) is the difference between numbers of nonnegative multiples of 2*n+1 with even and odd digit sum in base 2*n in interval [0, 128*n^7).

Crossrefs

Programs

  • Mathematica
    Table[(1/15) (8 n^2 - 4 n + 1) (16 n^3 + 48 n^2 + 32 n - 15), {n, 29}] (* Bruno Berselli, May 24 2012 *)
    LinearRecurrence[{6,-15,20,-15,6,-1},{27,615,3843,14351,40363,94711},30] (* Harvey P. Dale, Apr 30 2018 *)
  • PARI
    Vec(x*(27+453*x+558*x^2-22*x^3+7*x^4+x^5)/(1-x)^6 + O(x^50)) \\ Colin Barker, Dec 01 2015

Formula

a(n) = 2/(2*n+1)*Sum_{i=1..n} tan^7(Pi*i/(2*n+1))*sin(2*Pi*i/(2*n+1)).
G.f.: x*(27+453*x+558*x^2-22*x^3+7*x^4+x^5)/(1-x)^6. [Bruno Berselli, May 24 2012]

A014205 (1/12)*(n+5)*(n+1)*n^2.

Original entry on oeis.org

0, 1, 7, 24, 60, 125, 231, 392, 624, 945, 1375, 1936, 2652, 3549, 4655, 6000, 7616, 9537, 11799, 14440, 17500, 21021, 25047, 29624, 34800, 40625, 47151, 54432, 62524, 71485, 81375, 92256, 104192, 117249, 131495, 147000, 163836, 182077, 201799, 223080, 246000
Offset: 0

Views

Author

Keywords

Comments

Partial sums of A084990. - Arkadiusz Wesolowski, Jan 25 2014

Crossrefs

Cf. A084990.

Programs

  • Magma
    [(1/12)*(n+5)*(n+1)*n^2: n in [0..50]]; // Vincenzo Librandi, Aug 11 2014
    
  • Maple
    seq(2*binomial(n+3, 4)-binomial(n+1, 2), n=0..32); # Zerinvary Lajos, May 02 2007
  • Mathematica
    Table[((n+5)(n+1)n^2)/12,{n,0,40}] (* or *) LinearRecurrence[{5,-10,10,-5,1},{0,1,7,24,60},50] (* Harvey P. Dale, Aug 10 2014 *)
    CoefficientList[Series[x (x^2 - 2 x - 1)/(x - 1)^5, {x, 0, 50}], x] (* Vincenzo Librandi, Aug 11 2014 *)
  • PARI
    a(n)=n^2*(n+1)*(n+5)/12 \\ Charles R Greathouse IV, Oct 21 2022

Formula

a(n) = 2*C(n+3,4) - C(n+1,2). - Zerinvary Lajos, May 02 2007
G.f.: x*(x^2-2*x-1)/(x-1)^5. - Maksym Voznyy (voznyy(AT)mail.ru), Aug 10 2009
a(0)=0, a(1)=1, a(2)=7, a(3)=24, a(4)=60, a(n)=5*a(n-1)-10*a(n-2)+ 10*a(n-3)- 5*a(n-4)+a(n-5). - Harvey P. Dale, Aug 10 2014

A212705 a(n) is the difference between numbers of nonnegative multiples of 2*n+1 with even and odd digit sum in base 2*n in interval [0, (2*n)^8).

Original entry on oeis.org

54, 3220, 38794, 237832, 995710, 3256540, 8954258, 21645200, 47366982, 95758500, 181475866, 325939096, 559444366, 923676652, 1474657570, 2286163232, 3453646934, 5098701492, 7374096042, 10469422120, 14617383838
Offset: 1

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Author

Keywords

Crossrefs

Formula

a(n) = 2/(2*n+1)*sum{i=1..n}tan^8(pi*i/(2*n+1)).
a(n) = 2/315*n*(1088*n^6+3808*n^5+3920*n^4+280*n^3-868*n^2+322n-45).
G.f.: 2*x*(27+1394*x+7273*x^2+7308*x^3+1373*x^4+34*x^5-x^6)/(1-x)^8. [Bruno Berselli, May 24 2012]

A212706 a(n) is the difference between numbers of nonnegative multiples of 2*n+1 with even and odd digit sum in base 2*n in interval [0, (2*n)^9).

Original entry on oeis.org

81, 5825, 73745, 461313, 1951057, 6418369, 17712657, 42921473, 94087249, 190446273, 361259537, 649305089, 1115101521, 1841932225, 2941740049, 4561961985, 6893373521, 10179012289, 14724250641, 20908086785, 29195724113, 40152508353, 54459292177, 72929296897
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Magma
    [1+n/315*(4352*n^6+15232*n^5+12992*n^4-5600*n^3- 5152*n^2+5488*n-2112): n in [1..25]]; // Vincenzo Librandi, Dec 02 2015
  • Mathematica
    Table[1 + n/315 (4352 n^6 + 15232 n^5 + 12992 n^4 - 5600 n^3 - 5152 n^2 + 5488 n - 2112), {n, 30}] (* Vincenzo Librandi, Dec 02 2015 *)
    LinearRecurrence[{8,-28,56,-70,56,-28,8,-1},{81,5825,73745,461313,1951057,6418369,17712657,42921473},30] (* Harvey P. Dale, Aug 05 2025 *)
  • PARI
    Vec(x*(81+5177*x+29413*x^2+29917*x^3+4883*x^4+171*x^5-9*x^6-x^7)/(1-x)^8 + O(x^40)) \\ Colin Barker, Dec 01 2015
    

Formula

a(n) = 2/(2*n+1) * Sum_{i=1..n} tan^9(Pi*i/(2*n+1)) * sin(2*Pi*i/(2*n+1)).
a(n) = 1+n/315*(4352*n^6 + 15232*n^5 + 12992*n^4 - 5600*n^3 - 5152*n^2 + 5488*n - 2112).
G.f.: x*(81+5177*x+29413*x^2+29917*x^3+4883*x^4+171*x^5-9*x^6-x^7) / (1-x)^8. - Colin Barker, Dec 01 2015

Extensions

Typo in data fixed by Colin Barker, Dec 01 2015

A128226 Triangle, A004736 * A127899 (unsigned).

Original entry on oeis.org

1, 4, 2, 7, 7, 3, 10, 12, 10, 4, 13, 17, 17, 13, 5, 16, 22, 24, 22, 16, 6, 19, 27, 31, 31, 27, 19, 7, 22, 32, 38, 40, 38, 32, 22, 8, 25, 37, 45, 49, 49, 45, 37, 25, 9, 28, 42, 52, 58, 60, 58, 52, 42, 28, 10
Offset: 1

Views

Author

Gary W. Adamson, Feb 19 2007

Keywords

Comments

Row sums = A084990: (1, 6, 17, 36, 65, 106, ...).
A128225 = A127899(unsigned) * A004736.

Examples

			First few row of the triangle are:
   1;
   4,  2;
   7,  7,  3;
  10, 12, 10,  4;
  13, 17, 17, 13,  5;
  16, 22, 24, 22, 16,  6;
  19, 27, 31, 31, 27, 19,  7;
  ...
		

Crossrefs

Programs

  • Mathematica
    (* a127899U computes the unsigned version of A127899 *)
    a127899U[n_, k_] := If[n==k||n-1==k, n, 0]/;(1<=k<=n)
    a004736[n_, k_] := n-k+1/;(1<=k<=n+1)
    a128225[n_, k_] := a127899U[n, n](a004736[n, k] + a004736[n-1, k])/;(1<=k<=n)
    a128225[r_] := Table[a128225[n, k], {n, 1, r}, {k, 1, n}]
    TableForm[a128225[7]] (* triangle *)
    Flatten[a128225[10]] (* data *) (* Hartmut F. W. Hoft, Mar 13 2017 *)

Formula

A004736 * A127899 (unsigned). By columns, (3k+1), (5k+2), (7k+3), ...; k=0,1,2...

A131782 Triangle read by rows: (A004736 * A000012) + (A000012 * A004736) - A000012 as infinite lower triangular matrices.

Original entry on oeis.org

1, 5, 1, 11, 5, 1, 19, 11, 5, 1, 29, 19, 11, 5, 1, 41, 29, 19, 11, 5, 1, 55, 41, 29, 19, 11, 5, 1, 71, 55, 41, 29, 19, 11, 5, 1, 89, 71, 55, 41, 29, 19, 11, 5, 1, 109, 89, 71, 55, 41, 29, 19, 11, 5, 1, 131, 109, 89, 71, 55, 41, 29, 19, 11, 5, 1, 155, 131, 109, 89, 71, 55, 41, 29, 19, 11, 5, 1
Offset: 1

Views

Author

Gary W. Adamson, Jul 14 2007

Keywords

Comments

Row sums = A084990 starting (1, 6, 17, 36, 65, 106, ...).

Examples

			First few rows of the triangle:
   1;
   5,  1;
  11,  5,  1;
  19, 11,  5,  1;
  29, 19, 11,  5,  1;
  41, 29, 19, 11,  5,  1;
  55, 41, 29, 19, 11,  5,  1;
  ...
		

Crossrefs

Formula

n-th row = n descending terms of A028387: (1, 5, 11, 19, 29, 41, 55, ...). By columns, each column = A028387: (1, 5, 11, 19, 29, ...).

Extensions

Sign in definition and a(41) corrected; more terms from Georg Fischer, Jun 05 2023

A206492 Sums of rows of the sequence of triangles with nonnegative integers and row widths defined by A004738.

Original entry on oeis.org

0, 3, 3, 9, 21, 19, 11, 25, 45, 74, 66, 49, 26, 55, 90, 134, 190, 170, 138, 97, 50, 103, 162, 230, 310, 405, 365, 310, 243, 167, 85, 173, 267, 370, 485, 615, 763, 693, 605, 502, 387, 263, 133, 269, 411, 562, 725, 903, 1099, 1316, 1204, 1071, 920, 754, 576, 389
Offset: 1

Views

Author

Alex Ratushnyak, Jun 28 2012

Keywords

Comments

Row widths: A004738(n): 1, 2, 1, 2, 3, 2, 1, 2, 3, 4, 3, 2, 1, 2, 3, 4, 5...
Pits: A051925(n+1): 0, 3, 11, 26, 50, 85, 133, 196, 276, 375, 495, 638...
Peak tops: A007290(n+3): 2, 8, 20, 40, 70, 112, 168, 240, 330, 440, 572...
Peak bases: A084990(n+1): 1, 6, 17, 36, 65, 106, 161, 232, 321, 430, 561...

Examples

			The sequence of triangles begins:
0
1 2
3
4 5
6 7 8
9 10
11
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
		

Crossrefs

Cf. A027480: sums of rows of a triangle with increasing row widths: 0; 1,2; 3,4,5; 6,7,8,9; ...

Programs

  • Python
    curSign=-1
    curLength=sum=0
    rowLength=topLength=1
    for n in range(1232):
        sum += n
        curLength += 1
        if curLength==rowLength:
            print(sum, end=',')
            curLength = sum = 0
            if rowLength==1 or rowLength==topLength:
                curSign = -curSign
            topLength += (rowLength==1)
            rowLength += curSign
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