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 12 results. Next

A053698 a(n) = n^3 + n^2 + n + 1.

Original entry on oeis.org

1, 4, 15, 40, 85, 156, 259, 400, 585, 820, 1111, 1464, 1885, 2380, 2955, 3616, 4369, 5220, 6175, 7240, 8421, 9724, 11155, 12720, 14425, 16276, 18279, 20440, 22765, 25260, 27931, 30784, 33825, 37060, 40495, 44136, 47989, 52060, 56355, 60880
Offset: 0

Views

Author

Henry Bottomley, Mar 23 2000

Keywords

Comments

a(n) = 1111 in base n.
n^3 + n^2 + n + 1 = (n^2 + 1)*(n + 1), therefore a(n) is never prime. - Alonso del Arte, Apr 22 2014

Examples

			a(2) = 15 because 2^3 + 2^2 + 2 + 1 = 8 + 4 + 2 + 1 = 15.
a(3) = 40 because 3^3 + 3^2 + 3 + 1 = 27 + 9 + 3 + 1 = 40.
a(4) = 85 because 4^3 + 4^2 + 4 + 1 = 64 + 16 + 4 + 1 = 85.
From _Bruno Berselli_, Jan 02 2017: (Start)
The terms of the sequence are provided by the row sums of the following triangle (see the seventh formula in the previous section):
.   1;
.   3,   1;
.   9,   5,   1;
.  19,  13,   7,   1;
.  33,  25,  17,   9,   1;
.  51,  41,  31,  21,  11,   1;
.  73,  61,  49,  37,  25,  13,  1;
.  99,  85,  71,  57,  43,  29, 15,  1;
. 129, 113,  97,  81,  65,  49, 33, 17,  1;
. 163, 145, 127, 109,  91,  73, 55, 37, 19,  1;
. 201, 181, 161, 141, 121, 101, 81, 61, 41, 21, 1;
...
Columns from the first to the fifth, respectively: A058331, A001844, A056220 (after -1), A059993, A161532. Also, eighth column is A161549.
(End)
		

Crossrefs

Cf. A237627 (subset of semiprimes).
Cf. A056106 (first differences).

Programs

Formula

For n >= 2, a(n) = (n^4-1)/(n-1) = A024002(n)/A024000(n) = A002522(n)*(n+1) = A002061(n+1) + A000578(n).
G.f.: (1+5*x^2) / (1-x)^4. - Colin Barker, Jan 06 2012
a(n) = -A062158(-n). - Bruno Berselli, Jan 26 2016
a(n) = Sum_{i=0..n} 2*n*(n-i)+1. - Bruno Berselli, Jan 02 2017
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n > 3. - Colin Barker, Jan 02 2017
a(n) = A104878(n+3,n) = A055129(4,n) for n > 0. - Mathew Englander, Jan 06 2021
E.g.f.: exp(x)*(x^3+4*x^2+3*x+1). - Nikolaos Pantelidis, Feb 06 2023

A053699 a(n) = n^4 + n^3 + n^2 + n + 1.

Original entry on oeis.org

1, 5, 31, 121, 341, 781, 1555, 2801, 4681, 7381, 11111, 16105, 22621, 30941, 41371, 54241, 69905, 88741, 111151, 137561, 168421, 204205, 245411, 292561, 346201, 406901, 475255, 551881, 637421, 732541, 837931, 954305, 1082401, 1222981, 1376831, 1544761, 1727605
Offset: 0

Views

Author

Henry Bottomley, Mar 23 2000

Keywords

Comments

a(n) = 11111 in base n.
a(n) = Phi_5(n), where Phi_k is the k-th cyclotomic polynomial.

Crossrefs

5th row of the array A055129.
Cf. A104878.

Programs

Formula

a(n) = n^4 + n^3 + n^2 + n + 1 = (n^5-1)/(n-1).
G.f.: (1 + 16*x^2 + 6*x^3 + x^4)/(1-x)^5. - Colin Barker, Jan 10 2012
E.g.f.: exp(x)*(1 + 4*x + 11*x^2 + 7*x^3 + x^4). - Stefano Spezia, Oct 03 2024
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5). - Wesley Ivan Hurt, Aug 05 2025

A069777 Array of q-factorial numbers n!_q, read by ascending antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 6, 3, 1, 1, 1, 24, 21, 4, 1, 1, 1, 120, 315, 52, 5, 1, 1, 1, 720, 9765, 2080, 105, 6, 1, 1, 1, 5040, 615195, 251680, 8925, 186, 7, 1, 1, 1, 40320, 78129765, 91611520, 3043425, 29016, 301, 8, 1, 1
Offset: 0

Views

Author

Keywords

Examples

			Square array begins:
    1,   1,    1,      1,       1,        1,         1, ...
    1,   1,    1,      1,       1,        1,         1, ...
    1,   2,    3,      4,       5,        6,         7, ...
    1,   6,   21,     52,     105,      186,       301, ...
    1,  24,  315,   2080,    8925,    29016,     77959, ...
    1, 120, 9765, 251680, 3043425, 22661496, 121226245, ...
    ...
		

Crossrefs

Rows n=3..5 are A069778, A069779, A218503.
Main diagonal gives A347611.

Programs

  • Maple
    A069777 := proc(n,k) local n1: mul(A104878(n1,k), n1=k..n-1) end: A104878 := proc(n,k): if k = 0 then 1 elif k=1 then n elif k>=2 then (k^(n-k+1)-1)/(k-1) fi: end: seq(seq(A069777(n,k), k=0..n), n=0..9); # Johannes W. Meijer, Aug 21 2011
    nmax:=9: T(0,0):=1: for n from 1 to nmax do T(n,0):=1:  T(n,1):= (n-1)! od: for q from 2 to nmax do for n from 0 to nmax do T(n+q,q) := product((q^k - 1)/(q - 1), k= 1..n) od: od: for n from 0 to nmax do seq(T(n,k), k=0..n) od; seq(seq(T(n,k), k=0..n), n=0..nmax); # Johannes W. Meijer, Aug 21 2011
    # alternative Maple program:
    T:= proc(n, k) option remember; `if`(n<2, 1,
          T(n-1, k)*`if`(k=1, n, (k^n-1)/(k-1)))
        end:
    seq(seq(T(d-k, k), k=0..d), d=0..10);  # Alois P. Heinz, Sep 08 2021
  • Mathematica
    (* Returns the rectangular array *) Table[Table[QFactorial[n, q], {q, 0, 6}], {n, 0, 6}] (* Geoffrey Critzer, May 21 2017 *)
  • PARI
    T(n,q)=prod(k=1, n, ((q^k - 1) / (q - 1))) \\ Andrew Howroyd, Feb 19 2018

Formula

T(n,q) = Product_{k=1..n} (q^k - 1) / (q - 1).
T(n,k) = Product_{n1=k..n-1} A104878(n1,k). - Johannes W. Meijer, Aug 21 2011
T(n,k) = Sum_{i>=0} A008302(n,i)*k^i. - Geoffrey Critzer, Feb 26 2025

Extensions

Name edited by Michel Marcus, Sep 08 2021

A053716 a(n) = 1111111 in base n.

Original entry on oeis.org

7, 127, 1093, 5461, 19531, 55987, 137257, 299593, 597871, 1111111, 1948717, 3257437, 5229043, 8108731, 12204241, 17895697, 25646167, 36012943, 49659541, 67368421, 90054427, 118778947, 154764793, 199411801, 254313151, 321272407, 402321277, 499738093
Offset: 1

Views

Author

Henry Bottomley, Mar 23 2000

Keywords

Comments

Evaluation of the seventh cyclotomic polynomial at n. - Joerg Arndt, Aug 27 2015

Examples

			a(3)=1093 because 1111111 base 3=729+243+81+27+9+3+1=121.
		

Crossrefs

7th row of the array A055129.
Cf. A104878.

Programs

  • Magma
    [7] cat [(n^7-1)/(n-1): n in [2..35]]; // Vincenzo Librandi, Feb 08 2014
  • Maple
    A053716 := proc(n)
        numtheory[cyclotomic](7,n) ;
    end proc:
    seq(A053716(n),n=1..20) ; # R. J. Mathar, Feb 07 2014
  • Mathematica
    Table[FromDigits["1111111",n],{n,1,30}](*or*)Table[n^6+n^5+n^4+n^3+n^2+n+1,{n,1,60}] (* Vladimir Joseph Stephan Orlovsky, Jan 29 2012 *)
    CoefficientList[Series[-(x^6 - 6 x^5 + 57 x^4 + 232 x^3 + 351 x^2 + 78 x + 7)/(x - 1)^7, {x, 0, 40}], x] (* Vincenzo Librandi, Feb 08 2014 *)

Formula

a(n) = n^6+n^5+n^4+n^3+n^2+n+1 = (n^7-1)/(n-1).
G.f.: -x*(x^6-6*x^5+57*x^4+232*x^3+351*x^2+78*x+7)/(x-1)^7. - Colin Barker, Oct 29 2012
E.g.f.: exp(x)*(1 + 6*x + 57*x^2 + 122*x^3 + 76*x^4+ 16*x^5 + x^6) - 1. - Stefano Spezia, Oct 03 2024

A031973 a(n) = Sum_{k=0..n} n^k.

Original entry on oeis.org

1, 2, 7, 40, 341, 3906, 55987, 960800, 19173961, 435848050, 11111111111, 313842837672, 9726655034461, 328114698808274, 11966776581370171, 469172025408063616, 19676527011956855057, 878942778254232811938, 41660902667961039785743, 2088331858752553232964200
Offset: 0

Views

Author

Keywords

Comments

These are the generalized repunits of length n+1 in base n for all n >= 1: a(n) expressed in base n is 111...111 (n+1 1's): a(1) = 1^0 + 1^1 = 2 = A000042(2), a(2) = 2^0 + 2^1 + 2^2 = 7 = A000225(3), a(3) = 3^0 + 3^1 + 3^2 + 3^3 = 40 = A003462(4), etc., a(10) = 10^0 + 10^1 + 10^2 + ... + 10^9 + 10^10 = 11111111111 = A002275(11), etc. - Rick L. Shepherd, Aug 26 2004
a(n)=the total number of ordered selections of up to n objects from n types with repetitions allowed. Thus for 2 objects a,b there are 7 possible selections: aa,bb,ab,ba,a,b, and the null set. - J. M. Bergot, Mar 26 2014
a(n)=the total number of ordered arrangements of 0,1,2..n objects, with repetitions allowed, selected from n types of objects. - J. M. Bergot, Apr 11 2014

Examples

			a(3) = 3^0 + 3^1 + 3^2 + 3^3 = 40.
		

Crossrefs

Cf. A000042 (unary representations), A000225 (2^n-1: binary repunits shown in decimal), A003462 ((3^n-1)/2: ternary repunits shown in decimal), A002275 ((10^n-1)/9: decimal repunits).
Cf. A104878.

Programs

  • Magma
    [&+[n^k: k in [0..n]]: n in [0..30]]; // Vincenzo Librandi, Apr 18 2011
    
  • Maple
    a:= proc(n) local c, i; c:=1; for i to n do c:= c*n+1 od; c end:
    seq(a(n), n=0..20); # Alois P. Heinz, Aug 15 2013
  • Mathematica
    Join[{1},Table[Total[n^Range[0,n]],{n,20}]] (* Harvey P. Dale, Nov 13 2011 *)
  • PARI
    a(n)=(n^(n+1)-1)/(n-1) \\ Charles R Greathouse IV, Mar 26 2014
  • Sage
    [lucas_number1(n,n,n-1) for n in range(1, 19)] # Zerinvary Lajos, May 16 2009
    

Formula

a(n) = (n^(n+1)-1)/(n-1) = (A007778(n)-1)/(n-1) = A023037(n)+A000312(n) = A031972(n)+1. - Henry Bottomley, Apr 04 2003
a(n) = A125118(n,n-2) for n>2. - Reinhard Zumkeller, Nov 21 2006
a(n) = [x^n] 1/((1 - x)*(1 - n*x)). - Ilya Gutkovskiy, Oct 04 2017
a(n) = A104878(2n,n). - Alois P. Heinz, May 04 2021

A125118 Triangle read by rows: T(n,k) = value of the n-th repunit in base (k+1) representation, 1<=k<=n.

Original entry on oeis.org

1, 3, 4, 7, 13, 21, 15, 40, 85, 156, 31, 121, 341, 781, 1555, 63, 364, 1365, 3906, 9331, 19608, 127, 1093, 5461, 19531, 55987, 137257, 299593, 255, 3280, 21845, 97656, 335923, 960800, 2396745, 5380840, 511, 9841, 87381, 488281, 2015539, 6725601, 19173961, 48427561, 111111111
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 21 2006

Keywords

Examples

			First 4 rows:
1: [1]_2
2: [11]_2 ........ [11]_3
3: [111]_2 ....... [111]_3 ....... [111]_4
4: [1111]_2 ...... [1111]_3 ...... [1111]_4 ...... [1111]_5
_
1: 1
2: 2+1 ........... 3+1
3: (2+1)*2+1 ..... (3+1)*3+1 ..... (4+1)*4+1
4: ((2+1)*2+1)*2+1 ((3+1)*3+1)*3+1 ((4+1)*4+1)*4+1 ((5+1)*5+1)*5+1.
		

Crossrefs

This triangle shares some features with triangle A104878.
This triangle is a portion of rectangle A055129.
Each term of A110737 comes from the corresponding row of this triangle.
Diagonals (adjusting offset as necessary): A060072, A023037, A031973, A173468.
Cf. A023037, A031973, A125119, A125120 (row sums).

Programs

  • Magma
    [((k+1)^n -1)/k : k in [1..n], n in [1..12]]; // G. C. Greubel, Aug 15 2022
    
  • Mathematica
    Table[((k+1)^n -1)/k, {n, 12}, {k, n}]//Flatten (* G. C. Greubel, Aug 15 2022 *)
  • SageMath
    def A125118(n,k): return ((k+1)^n -1)/k
    flatten([[A125118(n,k) for k in (1..n)] for n in (1..12)]) # G. C. Greubel, Aug 15 2022

Formula

T(n, k) = Sum_{i=0..n-1} (k+1)^i.
T(n+1, k) = (k+1)*T(n, k) + 1.
Sum_{k=1..n} T(n, k) = A125120(n).
T(2*n-1, n) = A125119(n).
T(n, 1) = A000225(n).
T(n, 2) = A003462(n) for n>1.
T(n, 3) = A002450(n) for n>2.
T(n, 4) = A003463(n) for n>3.
T(n, 5) = A003464(n) for n>4.
T(n, 9) = A002275(n) for n>8.
T(n, n) = A060072(n+1).
T(n, n-1) = A023037(n) for n>1.
T(n, n-2) = A031973(n) for n>2.
T(n, k) = A055129(n, k+1) = A104878(n+k, k+1), 1<=k<=n. - Mathew Englander, Dec 19 2020

A053700 a(n) = 111111 in base n.

Original entry on oeis.org

6, 63, 364, 1365, 3906, 9331, 19608, 37449, 66430, 111111, 177156, 271453, 402234, 579195, 813616, 1118481, 1508598, 2000719, 2613660, 3368421, 4288306, 5399043, 6728904, 8308825, 10172526, 12356631, 14900788, 17847789, 21243690, 25137931
Offset: 1

Views

Author

Henry Bottomley, Mar 23 2000

Keywords

Examples

			a(3)=364 because 111111 base 3 = 243 + 81 + 27 + 9 + 3 + 1 = 121.
		

Crossrefs

6th row of the array A055129.
Cf. A104878.

Programs

Formula

a(n) = n^5 + n^4 + n^3 + n^2 + n + 1 = (n^6-1)/(n-1).
G.f.: x*(6 + 27*x + 76*x^2 + 6*x^3 + 6*x^4 - x^5)/(1-x)^6. - Colin Barker, May 08 2012
E.g.f.: exp(x)*(1 + 5*x + 26*x^2 + 32*x^3 + 11*x^4+ x^5) - 1. - Stefano Spezia, Oct 03 2024

A053717 a(n) = n^7 + n^6 + n^5 + n^4 + n^3 + n^2 + n + 1.

Original entry on oeis.org

1, 8, 255, 3280, 21845, 97656, 335923, 960800, 2396745, 5380840, 11111111, 21435888, 39089245, 67977560, 113522235, 183063616, 286331153, 435984840, 648232975, 943531280, 1347368421, 1891142968, 2613136835, 3559590240, 4785883225, 6357828776, 8353082583
Offset: 0

Views

Author

Henry Bottomley, Mar 23 2000

Keywords

Comments

a(n) = 11111111 in base n for n>0.

Examples

			a(3) = 3280 because 11111111 base 3 = 2187+729+243+81+27+9+3+1 = 3280.
		

Crossrefs

8th row of the array A055129.
Cf. A104878.

Programs

Formula

a(n) = (n^8-1)/(n-1) for n != 1.
G.f.: 1 -x*(x^7-8*x^6-57*x^5-1016*x^4-2297*x^3-1464*x^2-191*x-8)/(x-1)^8. - Colin Barker, Oct 29 2012
E.g.f.: exp(x)*(1 + 7*x + 120*x^2 + 423*x^3 + 426*x^4 + 156*x^5 + 22*x^6 + x^7). - Stefano Spezia, Oct 03 2024
a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8). - Wesley Ivan Hurt, Jun 19 2025

Extensions

a(0)=1 prepended by Alois P. Heinz, May 04 2021

A104879 Row sums of a sum-of-powers triangle.

Original entry on oeis.org

1, 2, 4, 8, 17, 40, 106, 316, 1049, 3830, 15208, 65072, 297841, 1449756, 7468542, 40555748, 231335961, 1381989882, 8623700812, 56078446616, 379233142801, 2662013133296, 19362917622002, 145719550012300, 1133023004941273, 9090156910550110, 75161929739797520
Offset: 0

Views

Author

Paul Barry, Mar 28 2005

Keywords

Crossrefs

Row sums of A104878.
Cf. A103439 (terms differ by 1), A026898 (first differences).

Formula

a(n) = 1 + n + Sum_{k=2..n+1} (k^(n-k+1)-1)/(k-1).
a(n) = 1 + A103439(n). - Mathew Englander, Dec 19 2020

A104881 Triangle T(n,k) = Sum_{j=0..k} (n-k)^(k-j), read by rows.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 3, 1, 1, 4, 7, 4, 1, 1, 5, 13, 15, 5, 1, 1, 6, 21, 40, 31, 6, 1, 1, 7, 31, 85, 121, 63, 7, 1, 1, 8, 43, 156, 341, 364, 127, 8, 1, 1, 9, 57, 259, 781, 1365, 1093, 255, 9, 1, 1, 10, 73, 400, 1555, 3906, 5461, 3280, 511, 10, 1, 1, 11, 91, 585, 2801, 9331, 19531, 21845, 9841, 1023, 11, 1
Offset: 0

Views

Author

Paul Barry, Mar 28 2005

Keywords

Comments

Reverse of triangle A104878.

Examples

			Triangle begins as:
  1;
  1, 1;
  1, 2,  1;
  1, 3,  3,  1;
  1, 4,  7,  4, 1;
  1, 5, 13, 15, 5, 1;
		

Crossrefs

Cf. A104878, A104879 (row sums), A104882 (diagonal sums).

Programs

  • Magma
    [(&+[ (n-k)^(k-j): j in [0..k]]): k in [0..n], n in [0..12]]; // G. C. Greubel, Jun 15 2021
    
  • Mathematica
    T[n_, k_]:= If[k==n, 1, Sum[(n-k)^(k-j), {j,0,k}]];
    Table[T[n, k], {n,0,12}, {k,0,n}]//Flatten (* G. C. Greubel, Jun 15 2021 *)
  • Sage
    flatten([[sum((n-k)^(k-j) for j in (0..k)) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Jun 15 2021

Formula

T(n, k) = Sum_{j=0..k} (n-k)^(k-j).
Sum_{k=0..n} T(n, k) = A104879(n).
Sum_{k=0..floor(n/2)} T(k, n-k) = A104882(n).
Showing 1-10 of 12 results. Next