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 1-8 of 8 results.

A005898 Centered cube numbers: n^3 + (n+1)^3.

Original entry on oeis.org

1, 9, 35, 91, 189, 341, 559, 855, 1241, 1729, 2331, 3059, 3925, 4941, 6119, 7471, 9009, 10745, 12691, 14859, 17261, 19909, 22815, 25991, 29449, 33201, 37259, 41635, 46341, 51389, 56791, 62559, 68705, 75241, 82179, 89531, 97309, 105525, 114191, 123319, 132921
Offset: 0

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Author

Keywords

Comments

Write the natural numbers in groups: 1; 2,3,4; 5,6,7,8,9; 10,11,12,13,14,15,16; ..... and add the groups, i.e., a(n) = Sum_{j=n^2-2(n-1)..n^2} j. - Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Sep 05 2001
The numbers 1, 9, 35, 91, etc. are divisible by 1, 3, 5, 7, etc. Therefore there are no prime numbers in this list. 9 is divisible by 3 and every third number after 9 is also divisible by 3. 35 is divisible by 5 and 7 and every fifth number after 35 is also divisible by 5 and every seventh number after 35 is also divisible by 7. This pattern continues indefinitely. - Howard Berman (howard_berman(AT)hotmail.com), Nov 07 2008
n^3 + (n+1)^3 = (2n+1)*(n^2+n+1), hence all terms are composite. - Zak Seidov, Feb 08 2011
This is the order of an n-ball centered at a node in the Kronecker product (or direct product) of three cycles, each of whose lengths is at least 2n+2. - Pranava K. Jha, Oct 10 2011
Positive y values of 4*x^3 - 3*x^2 = y^2. - Bruno Berselli, Apr 28 2018

References

  • John H. Conway and Richard K. Guy, The Book of Numbers, New York: Springer-Verlag, 1996. See p. 52.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

(1/12)*t*(2*n^3 - 3*n^2 + n) + 2*n - 1 for t = 2, 4, 6, ... gives A049480, A005894, A063488, A001845, A063489, A005898, A063490, A057813, A063491, A005902, A063492, A005917, A063493, A063494, A063495, A063496.
Partial sums of A005897.
The 28 uniform 3D tilings: cab: A299266, A299267; crs: A299268, A299269; fcu: A005901, A005902; fee: A299259, A299265; flu-e: A299272, A299273; fst: A299258, A299264; hal: A299274, A299275; hcp: A007899, A007202; hex: A005897, A005898; kag: A299256, A299262; lta: A008137, A299276; pcu: A005899, A001845; pcu-i: A299277, A299278; reo: A299279, A299280; reo-e: A299281, A299282; rho: A008137, A299276; sod: A005893, A005894; sve: A299255, A299261; svh: A299283, A299284; svj: A299254, A299260; svk: A010001, A063489; tca: A299285, A299286; tcd: A299287, A299288; tfs: A005899, A001845; tsi: A299289, A299290; ttw: A299257, A299263; ubt: A299291, A299292; bnn: A007899, A007202. See the Proserpio link in A299266 for overview.

Programs

Formula

a(n) = Sum_{i=0..n} A005897(i), partial sums. - Jonathan Vos Post, Feb 06 2011
G.f.: (x^2+4*x+1)*(1+x)/(1-x)^3. - Simon Plouffe (see MAPLE section) and Colin Barker, Jan 02 2012; edited by N. J. A. Sloane, Feb 07 2018
a(n) = A037270(n+1) - A037270(n). - Ivan N. Ianakiev, May 13 2012
a(n) = A000217(n+1)^2 - A000217(n-1)^2. - Bob Selcoe, Mar 25 2016
a(n) = A005408(n) * A002061(n+1). - Miquel Cerda, Oct 05 2016
From Ilya Gutkovskiy, Oct 06 2016: (Start)
E.g.f.: (1 + 8*x + 9*x^2 + 2*x^3)*exp(x).
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4). (End)
a(n) = (A081435(n))^2 - (A081435(n) - 1)^2. - Sergey Pavlov, Mar 01 2017

A081436 Fifth subdiagonal in array of n-gonal numbers A081422.

Original entry on oeis.org

1, 7, 24, 58, 115, 201, 322, 484, 693, 955, 1276, 1662, 2119, 2653, 3270, 3976, 4777, 5679, 6688, 7810, 9051, 10417, 11914, 13548, 15325, 17251, 19332, 21574, 23983, 26565, 29326, 32272, 35409, 38743, 42280, 46026, 49987, 54169, 58578, 63220
Offset: 0

Views

Author

Paul Barry, Mar 21 2003

Keywords

Comments

One of a family of sequences with palindromic generators.
Also as A(n) = (1/6)*(6*n^3 - 3*n^2 + 3*n), n>0: structured pentagonal diamond numbers (vertex structure 5). (Cf. A004068 = alternate vertex; A000447 = structured diamonds; A100145 for more on structured numbers.) - James A. Record (james.record(AT)gmail.com), Nov 07 2004
Sequence of the absolute values of the z^1 coefficients of the polynomials in the GF4 denominators of A156933. See A157705 for background information. - Johannes W. Meijer, Mar 07 2009
Row 1 of the convolution arrays A213831 and A213833. - Clark Kimberling, Jul 04 2012
Partial sums of A056109. - J. M. Bergot, Jun 22 2013
Number of ordered pairs of intersecting multisets of size 2, each chosen with repetition from {1,...,n}. - Robin Whitty, Feb 12 2014
Row sums of A244418. - L. Edson Jeffery, Jan 10 2015

Crossrefs

Programs

Formula

a(n) = (n+1)*(2*n^2 + 3*n + 2)/2.
G.f.: (1+x)*(1+2*x)/(1-x)^4. (Convolution of A005408 and A016777.)
a(n) = A110449(n, n-1), for n>1.
a(n) = (n+1)*T(n+1) + n*T(n), where T( ) are triangular numbers. Binomial transform of [1, 6, 11, 6, 0, 0, 0, ...]. - Gary W. Adamson, Dec 28 2007
E.g.f.: exp(x)*(2 + 12*x + 11*x^2 + 2*x^3)/2. - Stefano Spezia, Apr 13 2021
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4). - Wesley Ivan Hurt, Apr 14 2021

Extensions

G.f. simplified and crossrefs added by Johannes W. Meijer, Mar 07 2009

A213276 Number A(n,k) of n-length words w over a k-ary alphabet such that for every prefix z of w we have #(z,a_i) = 0 or #(z,a_i) >= #(z,a_j) for all j>i and #(z,a_i) counts the occurrences of the i-th letter in z; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 4, 1, 0, 1, 4, 9, 5, 1, 0, 1, 5, 16, 18, 9, 1, 0, 1, 6, 25, 46, 36, 14, 1, 0, 1, 7, 36, 95, 118, 74, 27, 1, 0, 1, 8, 49, 171, 315, 276, 165, 46, 1, 0, 1, 9, 64, 280, 711, 895, 712, 367, 91, 1, 0, 1, 10, 81, 428, 1414, 2506, 2535, 1805, 869, 162, 1, 0
Offset: 0

Views

Author

Alois P. Heinz, Jun 08 2012

Keywords

Examples

			A(0,k) = 1: the empty word.
A(n,1) = 1: (a)^n for alphabet {a}.
A(1,k) = k: number of words = size of the alphabet.
A(2,k) = k^2: all words with 2 letters from the alphabet.
A(3,2) = 5: aaa, aab, aba, baa, bbb for alphabet {a,b}.
A(3,3) = 18: aaa, aab, aac, aba, abc, aca, acb, baa, bac, bbb, bbc, bca, bcb, caa, cab, cba, cbb, ccc.
A(4,2) = 9: aaaa, aaab, aaba, aabb, abaa, abab, baaa, baab, bbbb.
A(5,2) = 14: aaaaa, aaaab, aaaba, aaabb, aabaa, aabab, aabba, abaaa, abaab, ababa, baaaa, baaab, baaba, bbbbb.
Square array A(n,k) begins:
  1, 1,  1,   1,    1,    1,     1,     1, ...
  0, 1,  2,   3,    4,    5,     6,     7, ...
  0, 1,  4,   9,   16,   25,    36,    49, ...
  0, 1,  5,  18,   46,   95,   171,   280, ...
  0, 1,  9,  36,  118,  315,   711,  1414, ...
  0, 1, 14,  74,  276,  895,  2506,  6104, ...
  0, 1, 27, 165,  712, 2535,  8151, 23527, ...
  0, 1, 46, 367, 1805, 7280, 25781, 83916, ...
		

Crossrefs

Programs

  • Maple
    A:= (n, k)-> h(n, k, 0, []):
    h:= proc(n, k, m, l) option remember;
          `if`(n=0 and k=0, b(l), `if`(k=0 or n>0 and n1     then for j from i+1 to nops(l) do
          if l[i]<=l[j] then return false
        elif l[j]>0     then break
          fi od fi; true
        end:
    seq(seq(A(n, d-n), n=0..d), d=0..14);
  • Mathematica
    a[n_, k_] := h[n, k, 0, {}];
    h[n_, k_, m_, l_] := h[n, k, m, l] = If[n == 0 && k === 0, b[l], If[k == 0 || n > 0 && n < m, 0, Sum[h[n-j, k-1, Max[m, j], Join[{j}, l]], {j, Max[1, m], n}] + h[n, k-1, m, Join[{0}, l]]]];
    b[l_] := b[l] = If[Complement[l, {0}] == {}, 1, Sum[If[g[l, i], b[ReplacePart[l, i -> l[[i]]-1]], 0], {i, 1, Length[l]}]];
    g[l_, i_] := Module[{j}, If[l[[i]] < 1, Return[False], If[l[[i]] > 1, For[ j = i+1, j <= Length[l], j++, If[l[[i]] <= l[[j]], Return[False], If[l[[j]] > 0, Break[]]]]]]; True];
    Table[Table[a[n, d-n], {n, 0, d}], {d, 0, 14}] // Flatten (* Jean-François Alcover, Dec 11 2013, translated from Maple *)

Formula

T(n,k) = Sum_{i=0..k} C(k,i) * A257783(n,k-i).

A081437 Diagonal in array of n-gonal numbers A081422.

Original entry on oeis.org

1, 10, 33, 76, 145, 246, 385, 568, 801, 1090, 1441, 1860, 2353, 2926, 3585, 4336, 5185, 6138, 7201, 8380, 9681, 11110, 12673, 14376, 16225, 18226, 20385, 22708, 25201, 27870, 30721, 33760, 36993, 40426, 44065, 47916, 51985, 56278, 60801, 65560
Offset: 0

Views

Author

Paul Barry, Mar 21 2003

Keywords

Comments

One of a family of sequences with palindromic generators.
For q a prime power, a(q-1) = q^3 + q^2 - q is the number of pairs of commuting nilpotent 2*2 matrices with coefficients in GF(q). (Proof: the zero matrix commutes with all q^2 nilpotent matrices, there are q^2-1 nonzero nilpotent matrices, all conjugate, each commuting with q nilpotent matrices.) - Mark Wildon, Jun 20 2017
Also the cyclomatic number (= circuit rank) of the n+1 X n+1 rook graph. - Eric W. Weisstein, Jun 20 2017

Crossrefs

Equals A027620(n-1) + 1.

Programs

  • GAP
    List([0..40], n-> (n+1)^3+n*(n+1)); # G. C. Greubel, Aug 14 2019
  • Magma
    [n^3+4*n^2+4*n+1: n in [0..50]]; // Vincenzo Librandi, Aug 08 2013
    
  • Maple
    a:=n->sum(n*k, k=0..n):seq(a(n)+sum(n*k, k=2..n), n=1..40); # Zerinvary Lajos, Jun 10 2008
    a:=n->sum(-2+sum(2+sum(2, j=1..n),j=1..n),j=1..n):seq(a(n)/2,n=1..40); # Zerinvary Lajos, Dec 06 2008
  • Mathematica
    Table[n^3 + 4 n^2 + 4n + 1, {n, 0, 40}] (* or *) LinearRecurrence[{4, -6, 4, -1}, {1, 10, 33, 76}, 40] (* Harvey P. Dale, Jan 24 2012 *)
    CoefficientList[Series[(1 + 5 x - 7 x^2 + x^3)/(1 - x)^5, {x, 0, 60}], x] (* Vincenzo Librandi, Aug 08 2013 *)
  • PARI
    vector(40, n, n--; (n+1)^3+n*(n+1)) \\ G. C. Greubel, Aug 14 2019
    
  • Sage
    [(n+1)^3+n*(n+1) for n in (0..40)] # G. C. Greubel, Aug 14 2019
    

Formula

a(n) = n^3 + 4*n^2 + 4*n + 1.
G.f.: (1 +5*x -7*x^2 +x^3)/(1-x)^5.
a(0)=1, a(1)=10, a(2)=33, a(3)=76; for n>3, a(n) = 4*a(n-1) -6*a(n-2) +4*a(n-3) -a(n-4). - Harvey P. Dale, Jan 24 2012
E.g.f.: (1 +9*x +7*x^2 +x^3)*exp(x). - G. C. Greubel, Aug 14 2019

A081422 Triangle read by rows in which row n consists of the first n+1 n-gonal numbers.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 1, 3, 6, 10, 1, 4, 9, 16, 25, 1, 5, 12, 22, 35, 51, 1, 6, 15, 28, 45, 66, 91, 1, 7, 18, 34, 55, 81, 112, 148, 1, 8, 21, 40, 65, 96, 133, 176, 225, 1, 9, 24, 46, 75, 111, 154, 204, 261, 325, 1, 10, 27, 52, 85, 126, 175, 232, 297, 370, 451
Offset: 0

Views

Author

Paul Barry, Mar 21 2003

Keywords

Examples

			The array starts
  1  1  3 10 ...
  1  2  6 16 ...
  1  3  9 22 ...
  1  4 12 28 ...
The triangle starts
  1;
  1,  1;
  1,  2,  3;
  1,  3,  6, 10;
  1,  4,  9, 16, 25;
  ...
		

Crossrefs

Antidiagonals are composed of n-gonal numbers.

Programs

  • GAP
    Flat(List([0..10], n-> List([1..n+1], k-> k*((n-2)*k-(n-4))/2 ))); # G. C. Greubel, Aug 14 2019
  • Magma
    [[k*((n-2)*k-(n-4))/2: k in [1..n+1]]: n in [0..10]]; // G. C. Greubel, Oct 13 2018
    
  • Mathematica
    Table[PolygonalNumber[n,i],{n,0,10},{i,n+1}]//Flatten (* Requires Mathematica version 10.4 or later *) (* Harvey P. Dale, Aug 27 2016 *)
  • PARI
    tabl(nn) = {for (n=0, nn, for (k=1, n+1, print1(k*((n-2)*k-(n-4))/2, ", ");); print(););} \\ Michel Marcus, Jun 22 2015
    
  • Sage
    [[k*((n-2)*k -(n-4))/2 for k in (1..n+1)] for n in (0..10)] # G. C. Greubel, Aug 14 2019
    

Formula

Array of coefficients of x in the expansions of T(k, x) = (1 + k*x -(k-2)*x^2)/(1-x)^4, k > -4.
T(n, k) = k*((n-2)*k -(n-4))/2 (see MathWorld link). - Michel Marcus, Jun 22 2015

A081423 Subdiagonal of array of n-gonal numbers A081422.

Original entry on oeis.org

1, 3, 12, 34, 75, 141, 238, 372, 549, 775, 1056, 1398, 1807, 2289, 2850, 3496, 4233, 5067, 6004, 7050, 8211, 9493, 10902, 12444, 14125, 15951, 17928, 20062, 22359, 24825, 27466, 30288, 33297, 36499, 39900, 43506, 47323, 51357, 55614, 60100
Offset: 0

Views

Author

Paul Barry, Mar 21 2003

Keywords

Comments

One of a family of sequences with palindromic generators.

Crossrefs

Programs

  • GAP
    List([0..40], n-> (2*n^3+n^2+n+2)/2); # G. C. Greubel, Aug 14 2019
  • Magma
    [(2*n^3+n^2+n+2)/2: n in [0..40]]; // Vincenzo Librandi, Aug 08 2013
    
  • Maple
    a := n-> (2*n^3+n^2+n+2)/2; seq(a(n), n = 0..40); # G. C. Greubel, Aug 14 2019
  • Mathematica
    CoefficientList[Series[(1 -2x +7x^2 -6x^3)/(1-x)^5, {x,0,40}], x] (* Vincenzo Librandi, Aug 08 2013 *)
  • PARI
    vector(40, n, n--; (2*n^3+n^2+n+2)/2) \\ G. C. Greubel, Aug 14 2019
    
  • Sage
    [(2*n^3+n^2+n+2)/2 for n in (0..40)] # G. C. Greubel, Aug 14 2019
    

Formula

a(n) = (2*n^3 + n^2 + n + 2)/2.
G.f.: (1 -2*x +7*x^2 -6*x^3)/(1-x)^5.
E.g.f.: (2 +4*x +7*x^2 +2*x^3)*exp(x)/2. - G. C. Greubel, Aug 14 2019

A147656 The arithmetic mean of the n-th and (n+1)-st cubes, rounded down.

Original entry on oeis.org

0, 4, 17, 45, 94, 170, 279, 427, 620, 864, 1165, 1529, 1962, 2470, 3059, 3735, 4504, 5372, 6345, 7429, 8630, 9954, 11407, 12995, 14724, 16600, 18629, 20817, 23170, 25694, 28395, 31279, 34352, 37620, 41089, 44765, 48654, 52762, 57095, 61659
Offset: 0

Views

Author

Keywords

Comments

The terms of this sequence relate to intervals between cubes in the same fashion as terms of A002378 are related to intervals between squares.

Crossrefs

Programs

  • Magma
    I:=[0, 4, 17, 45]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, May 06 2012
  • Maple
    seq(coeff(series(x*(x^2+x+4)/(1-x)^4,x,n+1), x, n), n = 0 .. 40); # Muniru A Asiru, Sep 11 2018
  • Mathematica
    Table[(n^3+(n+1)^3-1)/2,{n,0,70}] (* Vladimir Joseph Stephan Orlovsky, May 04 2011 *)
  • PARI
    j=[];for (n=0,40,j=concat(j,n^3+floor(((n+1)^3 - n^3)/2)));j
    
  • PARI
    a(n) = n*(2*n^2+3*n+3)/2; \\ Altug Alkan, Sep 20 2018
    

Formula

a(n) = floor((A000578(n) + A000578(n+1))/2).
From R. J. Mathar, Nov 11 2008: (Start)
a(n) = A000578(n) + A045943(n) = n*(2n^2+3n+3)/2.
G.f.: x*(4+x+x^2)/(1-x)^4. (End)
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4). - Vincenzo Librandi, May 06 2012
a(n) = A027480(n) + A006003(n). - Bruce J. Nicholson, Jun 03 2018
From A.H.M. Smeets, Sep 10 2018: (Start)
a(n) = Sum_{k=0..n-1} (n+1)^2-k for n >= 0 with empty domain of summation for n = 0.
a(n) = n*(n+1)^2 - n*(n-1)/2 for n >= 0.
Lim_{n -> inf} a(n-1)/n^3 = 1. (End)
E.g.f.: exp(x)*(8*x + 9*x^2 + 2*x^3)/2. - Stefano Spezia, Sep 12 2018
a(n) = A081435(n)-1. - R. J. Mathar, Sep 14 2018

A176798 Triangle read by rows: T(n,m)=1 + n*(2*m + 1 + n)/2, 0<=m<=n.

Original entry on oeis.org

1, 2, 3, 4, 6, 8, 7, 10, 13, 16, 11, 15, 19, 23, 27, 16, 21, 26, 31, 36, 41, 22, 28, 34, 40, 46, 52, 58, 29, 36, 43, 50, 57, 64, 71, 78, 37, 45, 53, 61, 69, 77, 85, 93, 101, 46, 55, 64, 73, 82, 91, 100, 109, 118, 127, 56, 66, 76, 86, 96, 106, 116, 126, 136, 146, 156
Offset: 0

Views

Author

Roger L. Bagula, Apr 26 2010

Keywords

Examples

			1;
2, 3;
4, 6, 8;
7, 10, 13, 16;
11, 15, 19, 23, 27;
16, 21, 26, 31, 36, 41;
22, 28, 34, 40, 46, 52, 58;
29, 36, 43, 50, 57, 64, 71, 78;
37, 45, 53, 61, 69, 77, 85, 93, 101;
46, 55, 64, 73, 82, 91, 100, 109, 118, 127;
56, 66, 76, 86, 96, 106, 116, 126, 136, 146, 156;
		

Crossrefs

Cf. A081435 (row sums), A104249 (diagonal).

Programs

  • Maple
    A176798 := proc(n,m)
        1+n*(2*m+1+n)/2 ;
    end proc: # R. J. Mathar, Feb 18 2016
  • Mathematica
    t[n_, m_] = 1 + n*(2*m + 1 + n)/2;
    Table[Table[t[n, m], {m, 0, n}], {n, 0, 10}];
    Flatten[%]
Showing 1-8 of 8 results.