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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A016974 a(n) = (6*n + 5)^6.

Original entry on oeis.org

15625, 1771561, 24137569, 148035889, 594823321, 1838265625, 4750104241, 10779215329, 22164361129, 42180533641, 75418890625, 128100283921, 208422380089, 326940373369, 496981290961, 735091890625, 1061520150601, 1500730351849, 2081951752609, 2839760855281, 3814697265625
Offset: 0

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Author

Keywords

Crossrefs

Subsequence of A001014 (n^6).

Programs

  • Magma
    [(6*n+5)^6: n in [0..25]]; // Vincenzo Librandi, May 10 2011
  • Mathematica
    (6Range[0,20]+5)^6 (* or *) LinearRecurrence[{7,-21,35,-35,21,-7,1},{15625,1771561,24137569,148035889,594823321,1838265625,4750104241},30] (* Harvey P. Dale, Apr 24 2025 *)

Formula

From Amiram Eldar, Apr 01 2022: (Start)
a(n) = A016969(n)^6 = A016970(n)^3 = A016971(n)^2.
Sum_{n>=0} 1/a(n) = PolyGamma(5, 5/6)/5598720. (End)

A101095 Fourth difference of fifth powers (A000584).

Original entry on oeis.org

1, 28, 121, 240, 360, 480, 600, 720, 840, 960, 1080, 1200, 1320, 1440, 1560, 1680, 1800, 1920, 2040, 2160, 2280, 2400, 2520, 2640, 2760, 2880, 3000, 3120, 3240, 3360, 3480, 3600, 3720, 3840, 3960, 4080, 4200, 4320, 4440, 4560, 4680, 4800, 4920, 5040, 5160, 5280
Offset: 1

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Author

Cecilia Rossiter, Dec 15 2004

Keywords

Comments

Original Name: Shells (nexus numbers) of shells of shells of shells of the power of 5.
The (Worpitzky/Euler/Pascal Cube) "MagicNKZ" algorithm is: MagicNKZ(n,k,z) = Sum_{j=0..k+1} (-1)^j*binomial(n + 1 - z, j)*(k - j + 1)^n, with k>=0, n>=1, z>=0. MagicNKZ is used to generate the n-th accumulation sequence of the z-th row of the Euler Triangle (A008292). For example, MagicNKZ(3,k,0) is the 3rd row of the Euler Triangle (followed by zeros) and MagicNKZ(10,k,1) is the partial sums of the 10th row of the Euler Triangle. This sequence is MagicNKZ(5,k-1,2).

Crossrefs

Fourth differences of A000584, third differences of A022521, second differences of A101098, and first differences of A101096.
For other sequences based upon MagicNKZ(n,k,z):
...... | n = 1 | n = 2 | n = 3 | n = 4 | n = 5 | n = 6 | n = 7 | n = 8
--------------------------------------------------------------------------------------
z = 0 | A000007 | A019590 | ....... MagicNKZ(n,k,0) = T(n,k+1) from A008292 .......
z = 1 | A000012 | A040000 | A101101 | A101104 | A101100 | ....... | ....... | .......
z = 2 | A000027 | A005408 | A008458 | A101103 | thisSeq | ....... | ....... | .......
z = 3 | A000217 | A000290 | A003215 | A005914 | A101096 | ....... | ....... | .......
z = 4 | A000292 | A000330 | A000578 | A005917 | A101098 | ....... | ....... | .......
z = 5 | A000332 | A002415 | A000537 | A000583 | A022521 | ....... | A255181 | .......
z = 12 | A001288 | A057788 | ....... | A254870 | A254471 | A254683 | A254646 | A254642
z = 13 | A010965 | ....... | ....... | ....... | A254871 | A254472 | A254684 | A254647
z = 14 | A010966 | ....... | ....... | ....... | ....... | A254872 | ....... | .......
--------------------------------------------------------------------------------------
Cf. A047969.

Programs

  • Magma
    I:=[1,28,121,240,360]; [n le 5 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]]; // Vincenzo Librandi, May 07 2015
    
  • Mathematica
    MagicNKZ=Sum[(-1)^j*Binomial[n+1-z, j]*(k-j+1)^n, {j, 0, k+1}];Table[MagicNKZ, {n, 5, 5}, {z, 2, 2}, {k, 0, 34}]
    CoefficientList[Series[(1 + 26 x + 66 x^2 + 26 x^3 + x^4)/(1 - x)^2, {x, 0, 50}], x] (* Vincenzo Librandi, May 07 2015 *)
    Join[{1,28,121,240},Differences[Range[50]^5,4]] (* or *) LinearRecurrence[{2,-1},{1,28,121,240,360},50] (* Harvey P. Dale, Jun 11 2016 *)
  • PARI
    a(n)=if(n>3, 120*n-240, 33*n^2-72*n+40) \\ Charles R Greathouse IV, Oct 11 2015
  • Sage
    [1,28,121]+[120*(k-2) for k in range(4,36)] # Danny Rorabaugh, Apr 23 2015
    

Formula

a(k+1) = Sum_{j=0..k+1} (-1)^j*binomial(n + 1 - z, j)*(k - j + 1)^n; n = 5, z = 2.
For k>3, a(k) = Sum_{j=0..4} (-1)^j*binomial(4, j)*(k - j)^5 = 120*(k - 2).
a(n) = 2*a(n-1) - a(n-2), n>5. G.f.: x*(1+26*x+66*x^2+26*x^3+x^4) / (1-x)^2. - Colin Barker, Mar 01 2012

Extensions

MagicNKZ material edited, Crossrefs table added, SeriesAtLevelR material removed by Danny Rorabaugh, Apr 23 2015
Name changed and keyword 'uned' removed by Danny Rorabaugh, May 06 2015

A106318 Bhaskara twins: n such that 2*n^2 = X^3 and 2*n^3 = Y^2.

Original entry on oeis.org

2, 128, 1458, 8192, 31250, 93312, 235298, 524288, 1062882, 2000000, 3543122, 5971968, 9653618, 15059072, 22781250, 33554432, 48275138, 68024448, 94091762, 128000000, 171532242, 226759808, 296071778, 382205952, 488281250, 617831552
Offset: 1

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Author

Lekraj Beedassy, Apr 29 2005

Keywords

References

  • S. S. Gupta, 'Bhaskara Pairs' in 'Science Today' (subsequently renamed '2001'), January 1988, pp. 68, Times of India, Mumbai.

Crossrefs

Programs

Formula

a(n) = 2*n^6 = 2*A001014(n).
G.f.: 2*(1+x)*(1+56*x+246*x^2+56*x^3+x^4)/(1-x)^7. - Colin Barker, Apr 18 2012
a(n) = 7*a(n-1)-21*a(n-2)+35*a(n-3)-35*a(n-4)+21*a(n-5)-7*a(n-6)+a(n-7). - Wesley Ivan Hurt, Apr 23 2021

A113851 Numbers whose prime factors are raised to the sixth power.

Original entry on oeis.org

64, 729, 15625, 46656, 117649, 1000000, 1771561, 4826809, 7529536, 11390625, 24137569, 47045881, 85766121, 113379904, 148035889, 308915776, 594823321, 729000000, 887503681, 1291467969, 1544804416, 1838265625, 2565726409, 3010936384, 3518743761, 4750104241
Offset: 1

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Author

Cino Hilliard, Jan 25 2006

Keywords

Crossrefs

Subset of A001014. Superset of A030516.
Nonunit terms of A329332 column 6 in ascending order.

Programs

  • Maple
    for n from 2 to 100 do if(numtheory[issqrfree](n))then printf("%d, ", n^6): fi: od: # Nathaniel Johnston, Jun 21 2011
  • Mathematica
    Select[ Range@37^6, Union[Last /@ FactorInteger@# ] == {6} &] (* Robert G. Wilson v *)
    Select[Range[2, 37], SquareFreeQ]^6 (* Amiram Eldar, Oct 13 2020 *)
  • Python
    from math import isqrt
    from sympy import mobius
    def A113851(n):
        def f(x): return int(n+1-sum(mobius(k)*(x//k**2) for k in range(2, isqrt(x)+1)))
        m, k = n, f(n)
        while m != k: m, k = k, f(k)
        return m**6 # Chai Wah Wu, Feb 25 2025

Formula

a(n) = A005117(n+1)^6. - Nathaniel Johnston, Jun 21 2011
Sum_{n>=1} 1/a(n) = zeta(6)/zeta(12) - 1 = A269404 - 1. - Amiram Eldar, Oct 13 2020

Extensions

More terms from Robert G. Wilson v, Jan 26 2006

A271099 Number of ordered ways to write n as u^3 + v^3 + 2*x^3 + 2*y^3 + 3*z^3, where u, v, x, y and z are nonnegative integers with u <= v and x <= y.

Original entry on oeis.org

1, 1, 2, 2, 3, 3, 2, 2, 2, 2, 1, 2, 2, 2, 1, 1, 3, 1, 3, 3, 3, 3, 1, 2, 2, 2, 3, 4, 4, 3, 4, 2, 5, 3, 4, 5, 2, 4, 1, 1, 4, 2, 4, 3, 4, 1, 2, 1, 3, 2, 1, 4, 1, 2, 4, 2, 7, 4, 5, 5, 2, 3, 2, 3, 3, 4, 2, 5, 4, 3, 6
Offset: 0

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Author

Zhi-Wei Sun, Mar 30 2016

Keywords

Comments

Conjecture: (i) a(n) > 0 for all n = 0,1,2,..., and a(n) = 1 only for n = 0, 1, 10, 14, 15, 17, 22, 38, 39, 45, 47, 50, 52, 76, 102, 103, 188, 295, 366, 534.
(ii) Any natural number n can be written as s^4 + t^4 + 2*u^4 + 2*v^4 + 3*x^4 + 3*y^4 + 7*z^4, where s, t, u, v, x, y and z are nonnegative integers. Also, each natural number n can be written as r^5 + s^5 + t^5 + u^5 + 2*v^5 + 4*w^5 + 6*x^5 + 9*y^5 +12*z^5, where r, s, t, u, v, w, x, y and z are nonnegative integers.
(iii) In general, for any integer k > 2, there are 2*k-1 positive integers c(1), c(2), ..., c(2k-1) such that {c(1)*x(1)^k + c(2)*x(2)^k + ... + c(2k-1)*x(2k-1)^k: x(1),x(2),...,x(k) = 0,1,2,...} = {0,1,2,3,...} and that c(1)+c(2)+...+c(2k-1) = g(k), where g(k) = 2^k+floor((3/2)^k)-2 as given by A002804.
This conjecture is stronger than the classical Waring problem on sums of k-th powers. Concerning parts (i) and (ii) of the conjecture, we note that 1+1+2+2+3 = 9 = g(3), 1+1+2+2+3+3+7 = 19 = g(4) and 1+1+1+1+2+4+6+9+12 = 37 = g(5).
We have verified that a(n) > 0 for all n = 0..10^6, and that part (ii) of the conjecture holds for n up to 10^5. Concerning part (iii) for k = 6, we conjecture that any natural number can be written as x(1)^6+x(2)^6+x(3)^6+x(4)^6+x(5)^6+3*x(6)^6+5*x(7)^6+6*x(8)^6+10*x(9)^6+18*x(10)^6+26*x(11)^6 with x(1),x(2),...,x(11) nonnegative integers. Note that 1+1+1+1+1+3+5+6+10+18+26 = 73 = g(6). - Zhi-Wei Sun, Mar 31 2016

Examples

			a(1) = 1 since 1 = 0^3 + 1^3 + 2*0^3 + 2*0^3 + 3*0^3.
a(10) = 1 since 10 = 0^3 + 2^3 + 2*0^3 + 2*1^3 + 3*0^3.
a(14) = 1 since 14 = 1^3 + 2^3 + 2*0^3 + 2*1^3 + 3*1^3.
a(15) = 1 since 15 = 0^3 + 2^3 + 2*1^3 + 2*1^3 + 3*1^3.
a(17) = 1 since 17 = 0^3 + 1^3 + 2*0^3 + 2*2^3 + 3*0^3.
a(22) = 1 since 22 = 0^3 + 1^3 + 2*1^3 + 2*2^3 + 3*1^3.
a(38) = 1 since 38 = 2^3 + 3^3 + 2*0^3 + 2*0^3 + 3*1^3.
a(39) = 1 since 39 = 2^3 + 3^3 + 2*1^3 + 2*1^3 + 3*0^3.
a(45) = 1 since 45 = 0^3 + 3^3 + 2*1^3 + 2*2^3 + 3*0^3.
a(47) = 1 since 47 = 1^3 + 3^3 + 2*0^3 + 2*2^3 + 3*1^3.
a(50) = 1 since 50 = 0^3 + 2^3 + 2*1^3 + 2*2^3 + 3*2^3.
a(52) = 1 since 52 = 1^3 + 3^3 + 2*0^3 + 2*0^3 + 3*2^3.
a(76) = 1 since 76 = 2^3 + 4^3 + 2*1^3 +2*1^3 + 3*0^3.
a(102) = 1 since 102 = 0^3 + 2^3 + 2*2^3 + 2*3^3 + 3*2^3.
a(103) = 1 since 103 = 1^3 + 2^3 + 2*2^3 + 2*3^3 + 3*2^3.
a(188) = 1 since 188 = 3^3 + 4^3 + 2*0^3 + 2*2^3 + 3*3^3.
a(295) = 1 since 295 = 1^3 + 6^3 + 2*0^3 + 2*3^3 + 3*2^3.
a(366) = 1 since 366 = 2^3 + 3^3 + 2*0^3 + 2*5^3 + 3*3^3.
a(534) = 1 since 534 = 1^3 + 8^3 + 2*1^3 + 2*2^3 + 3*1^3.
		

References

  • M. B. Nathanson, Additive Number Theory: The Classical Bases, Grad. Texts in Math., Vol 164, Springer, 1996, Chapters 2 and 3.

Crossrefs

Programs

  • Mathematica
    CQ[n_]:=CQ[n]=IntegerQ[n^(1/3)]
    Do[r=0;Do[If[CQ[n-3z^3-2x^3-2y^3-u^3],r=r+1],{z,0,(n/3)^(1/3)},{x,0,((n-3z^3)/4)^(1/3)},{y,x,((n-3z^3-2x^3)/2)^(1/3)},{u,0,((n-3z^3-2x^3-2y^3)/2)^(1/3)}];Print[n," ",r];Continue,{n,0,70}]

A001120 a(0) = a(1) = 1; for n > 1, a(n) = n*a(n-1) + (-1)^n.

Original entry on oeis.org

1, 1, 3, 8, 33, 164, 985, 6894, 55153, 496376, 4963761, 54601370, 655216441, 8517813732, 119249392249, 1788740883734, 28619854139745, 486537520375664, 8757675366761953, 166395831968477106, 3327916639369542121, 69886249426760384540, 1537497487388728459881
Offset: 0

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Author

Keywords

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

A000166 has a similar recurrence.
Column k=1 of A334715.
Cf. A000142.

Programs

  • Maple
    a:= proc(n) option remember;
         `if`(n<2, 1, n*a(n-1)+(-1)^n)
        end:
    seq(a(n), n=0..23);  # Alois P. Heinz, May 09 2020
  • Mathematica
    t = {1}; Do[AppendTo[t, n*t[[-1]] + (-1)^n], {n, 2, 20}]; t (* T. D. Noe, Jun 26 2012 *)
    RecurrenceTable[{a[1]==1,a[n]==n a[n-1]+(-1)^n},a,{n,30}] (* Harvey P. Dale, Feb 19 2018 *)
  • PARI
    a(n)=if(n<2,n>0,n*a(n-1)+(-1)^n)
    
  • PARI
    a(n)=if(n<1,0,n!*polcoeff((1+exp(-x+x*O(x^n)))/(1-x),n))

Formula

Nearest integer to n!(1+1/e).
a(n) = A000166(n) + [n > 0] * n!. - Philippe Deléham, Sep 04 2005
a(n) = (n-1)*(a(n-1)+a(n-2)), n>2. - Gary Detlefs, Apr 11 2010
E.g.f.: (exp(x)*x+1)*exp(-x)/(1-x). - Alois P. Heinz, May 08 2020

Extensions

a(0)=1 prepended by Alois P. Heinz, May 08 2020

A002604 a(n) = n^6 + 1.

Original entry on oeis.org

1, 2, 65, 730, 4097, 15626, 46657, 117650, 262145, 531442, 1000001, 1771562, 2985985, 4826810, 7529537, 11390626, 16777217, 24137570, 34012225, 47045882, 64000001, 85766122, 113379905, 148035890
Offset: 0

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Author

Keywords

Comments

Because of Fermat's little theorem, a(n) is never divisible by 7. - Altug Alkan, Apr 08 2016

Crossrefs

Equals A001014 + 1. Cf. A024004, A002522.

Programs

Formula

G.f. (-1 + 5*x - 72*x^2 - 282*x^3 - 317*x^4 - 51*x^5 - 2*x^6) / (x - 1)^7. - R. J. Mathar, Aug 06 2012
Sum_{n>=0} 1/a(n) = 1/2 + Pi * (coth(Pi) + (sinh(Pi) + sqrt(3)*sin(sqrt(3)*Pi)) / (cosh(Pi) - cos(sqrt(3)*Pi))) / 6 = 1.5171007340332164261529... . - Vaclav Kotesovec, Feb 14 2015
Sum_{n>=0} (-1)^n/a(n) = 1/2 + Pi/(6*sinh(Pi)) + Pi * (sqrt(3)*cosh(Pi/2) * sin((sqrt(3)*Pi)/2) + cos((sqrt(3)*Pi)/2) * sinh(Pi/2)) / (3*(cosh(Pi) - cos(sqrt(3)*Pi))) = 0.514210347292695053493... . - Vaclav Kotesovec, Feb 14 2015

A080761 Positive numbers of the form y^2 - x^3, x and y >= 1.

Original entry on oeis.org

1, 3, 8, 9, 12, 15, 17, 18, 19, 22, 24, 28, 30, 35, 36, 37, 38, 40, 41, 44, 48, 54, 55, 56, 57, 63, 64, 65, 68, 71, 73, 79, 80, 89, 92, 94, 97, 98, 99, 100, 101, 105, 106, 107, 108, 112, 113, 117, 119, 120, 121, 128, 129, 131, 132, 136, 138, 141, 142, 143, 145, 148, 151
Offset: 1

Views

Author

Cino Hilliard, Mar 10 2003

Keywords

Comments

From Artur Jasinski, Oct 03 2007: (Start)
Some numbers have multiple partitions:
8 = 4^2 - 8^3 = 312^2 - 46^3,
9 = 6^2 - 3^3 = 15^2 - 6 ^3 = 253^2 - 40^3. (End)
This is Mordell's equation with the condition that x and y are positive. Sequence A054504 lists the n for which there is no solution to Mordell's equation. Hence, none of those numbers will be in this sequence. The terms of this sequence can be determined by looking at the link to Gebel's data. - T. D. Noe, Mar 23 2011

Examples

			8 is in the sequence since 3^2 = 1^3 + 8.
		

Crossrefs

Complement of A080762.
Cf. sequences for n^3+7, n^3+17, n^3+3, n^3+2, n^3+5.

Programs

  • Mathematica
    With[{nn=100},Take[Union[Select[First[#]^2-Last[#]^3&/@Tuples[Range[ 20nn],2],#>0&]],nn]] (* Harvey P. Dale, Jul 10 2012 *)
  • PARI
    diop(n,m) = { for(p=1,m, for(x=1,n, y=x*x*x+p; if(issquare(y),print1(p" "); break) ) ) }

Extensions

"Positive" added to definition by N. J. A. Sloane, Oct 06 2007

A085539 a(n) = n^6 - n^5.

Original entry on oeis.org

0, 0, 32, 486, 3072, 12500, 38880, 100842, 229376, 472392, 900000, 1610510, 2737152, 4455516, 6991712, 10631250, 15728640, 22717712, 32122656, 44569782, 60800000, 81682020, 108226272, 141599546, 183140352, 234375000, 297034400, 373071582, 464679936
Offset: 0

Views

Author

N. J. A. Sloane, Jul 05 2003

Keywords

Comments

For n>=1, a(n) is equal to the number of functions f:{1,2,3,4,5,6}->{1,2,...,n} such that for a fixed x in {1,2,3,4,5,6} and a fixed y in {1,2,...,n} we have f(x)<>y. - Aleksandar M. Janjic and Milan Janjic, Mar 13 2007

Crossrefs

A diagonal of A228273.

Programs

Formula

G.f.: -2*x^2*(x^4+41*x^3+171*x^2+131*x+16)/(x-1)^7. - Colin Barker, Nov 06 2012
Sum_{n>=2} 1/a(n) = 5 - Sum_{k=2..5} zeta(k). - Amiram Eldar, Jul 05 2020

A163285 Triangle read by rows in which row n lists n+1 terms, starting with n^5 and ending with n^6, such that the difference between successive terms is equal to n^5 - n^4.

Original entry on oeis.org

0, 1, 1, 32, 48, 64, 243, 405, 567, 729, 1024, 1792, 2560, 3328, 4096, 3125, 5625, 8125, 10625, 13125, 15625, 7776, 14256, 20736, 27216, 33696, 40176, 46656, 16807, 31213, 45619, 60025, 74431, 88837, 103243, 117649, 32768, 61440, 90112, 118784, 147456
Offset: 0

Views

Author

Omar E. Pol, Jul 24 2009

Keywords

Comments

The first term of row n is A000584(n) and the last term of row n is A001014(n).
The main entry for this sequence is A159797. See also A163282, A163283 and A163284.
Row sums give A163275. - Omar E. Pol, Mar 18 2012

Examples

			Triangle begins:
0;
1,1;
32,48,64;
243,405,567,729;
1024,1792,2560,3328,4096;
3125,5625,8125,10625,13125,15625;
7776,14256,20736,27216,33696,40176,46656;
16807,31213,45619,60025,74431,88837,103243,117649;
32768,61440,90112,118784,147456,176128,204800,233472,262144;
59049,111537,164025,216513,269001,321489,373977,426465,478953,531441;
100000,190000,280000,370000,460000,550000,640000,730000,820000,910000,1000000;
		

Crossrefs

Programs

  • Mathematica
    rw[n_]:=Range[n^5,n^6,n^5-n^4]; Join[{0,1},Flatten[Array[rw,10]]] (* Harvey P. Dale, Mar 18 2012 *)
  • PARI
    A163285(n, k)=n^5 +k*(n^5 -n^4) \\ G. C. Greubel, Dec 17 2016
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