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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A259410 a(n) = 1 - sigma(n) + sigma(n)^2 - sigma(n)^3 + sigma(n)^4.

Original entry on oeis.org

1, 61, 205, 2101, 1111, 19141, 3641, 47461, 26521, 99451, 19141, 593461, 35855, 318505, 318505, 894661, 99451, 2255605, 152381, 3039331, 1016801, 1634221, 318505, 12747541, 894661, 3039331, 2497561, 9661961, 783871, 26505721, 1016801, 15506821, 5200081
Offset: 1

Views

Author

Robert Price, Jun 26 2015

Keywords

Crossrefs

Cf. A000203 (sum of divisors of n).
Cf. A259411 (indices of primes in this sequence), A259412 (corresponding primes).

Programs

  • Magma
    [(1 - DivisorSigma(1, n) + DivisorSigma(1, n)^2 - DivisorSigma(1, n)^3 + DivisorSigma(1, n)^4): n in [1..35]]; // Vincenzo Librandi, Jun 27 2015
  • Mathematica
    Table[1 - DivisorSigma[1, n] + DivisorSigma[1, n]^2 - DivisorSigma[1, n]^3 + DivisorSigma[1, n]^4, {n, 1, 10000}]
    Table[Cyclotomic[10, DivisorSigma[1, n]], {n, 1, 10000}]
  • PARI
    a(n) = polcyclo(10, sigma(n)) \\ Michel Marcus, Jun 26 2015
    

Formula

a(n) = 1 - A000203(n) + A000203(n)^2 - A000203(n)^3 + A000203(n)^4.
a(n) = A060884(A000203(n)). - Michel Marcus, Jun 26 2015

A020518 10th cyclotomic polynomial evaluated at powers of 2.

Original entry on oeis.org

1, 11, 205, 3641, 61681, 1016801, 16519105, 266354561, 4278255361, 68585520641, 1098438933505, 17583600302081, 281406274007041, 4503049938657281, 72053196259835905, 1152886321308467201, 18446462603027742721, 295145653396718878721, 4722348468539854946305
Offset: 0

Views

Author

Keywords

Crossrefs

Programs

  • Maple
    with(numtheory,cyclotomic):seq(cyclotomic(10,2^i),i=0..24);
  • Mathematica
    Cyclotomic[10, 2^Range[0, 20]] (* Paolo Xausa, Sep 16 2024 *)
  • PARI
    a(n) = polcyclo(10, 2^n) \\ Colin Barker, Feb 14 2015

Formula

G.f.: -(704*x^4-544*x^3+174*x^2-20*x+1) / ((x-1)*(2*x-1)*(4*x-1)*(8*x-1)*(16*x-1)). - Colin Barker, Feb 14 2015
a(n) = 1-2^n+4^n-8^n+16^n. - Colin Barker, Feb 15 2015
a(n) = A060884(A000079(n)). - Michel Marcus, Apr 06 2016

Extensions

More terms from Colin Barker, Feb 14 2015

A362783 Square array A(n,k) = (n^(2*k + 1) + 1)/(n + 1), n >= 0, k >= 0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 11, 7, 1, 1, 1, 43, 61, 13, 1, 1, 1, 171, 547, 205, 21, 1, 1, 1, 683, 4921, 3277, 521, 31, 1, 1, 1, 2731, 44287, 52429, 13021, 1111, 43, 1, 1, 1, 10923, 398581, 838861, 325521, 39991, 2101, 57, 1, 1, 1, 43691, 3587227, 13421773, 8138021, 1439671
Offset: 0

Views

Author

Juri-Stepan Gerasimov, May 03 2023

Keywords

Examples

			Array begins:
=====================================================================
n/k |  0    1      2       3         4          5            6   ...
----+----------------------------------------------------------------
0   |  1    1      1       1         1          1            1   ...
1   |  1    1      1       1         1          1            1   ...
2   |  1    3     11      43       171        683         2731   ...
3   |  1    7     61     547      4921      44287       398581   ...
4   |  1   13    205    3277     52429     838861     13421773   ...
5   |  1   21    521   13021    325521    8138021    203450521   ...
6   |  1   31   1111   39991   1439671   51828151   1865813431   ...
   ...
		

Crossrefs

Columns k=0..3 are A000012, A002061, A060884, A060888.
Rows n=2..4 are A007583, A066443, A299960.
Main diagonal is A179897.

Programs

  • Magma
    /* as array */ [[&+[(-n)^j: j in [0..2*k]]: k in [0..6]]: n in [0..6]]; // Juri-Stepan Gerasimov, May 06 2023
  • PARI
    A(n,k) = (n^(2*k + 1) + 1)/(n + 1) \\ Andrew Howroyd, May 03 2023
    

Formula

A(n,k) = Sum_{j=0..2*k} (-n)^j.

Extensions

a(49) corrected by Andrew Howroyd, Jan 20 2024

A191012 a(n) = n^5 - n^4 + n^3 - n^2 + n.

Original entry on oeis.org

0, 1, 22, 183, 820, 2605, 6666, 14707, 29128, 53145, 90910, 147631, 229692, 344773, 501970, 711915, 986896, 1340977, 1790118, 2352295, 3047620, 3898461, 4929562, 6168163, 7644120, 9390025, 11441326, 13836447, 16616908, 19827445
Offset: 0

Views

Author

Franz Vrabec, Jun 16 2011

Keywords

Comments

n such that x^5 + x^4 + x^3 + x^2 + x + n factors over the integers.

Examples

			a(2) = 22 is in the sequence, because x^5 + x^4 + x^3 + x^2 + x + 22 = (x+2)*(x^4 - x^3 + 3*x^2 - 5*x + 11).
		

Crossrefs

Cf. A060884.

Programs

  • Magma
    [n^5 - n^4 + n^3 - n^2 + n: n in [0..30]]; // Vincenzo Librandi, Jun 18 2011
  • Maple
    [seq(n*(n^4-n^3+n^2-n+1),n=0..25)];
  • PARI
    a(n)=((((n-1)*n+1)*n-1)*n+1)*n \\ Charles R Greathouse IV, Jun 17 2011
    

Formula

a(n) = n*A060884(n).
G.f.: x*(5*x^4 + 32*x^3 + 66*x^2 + 16*x + 1)/(1-x)^6.

A260077 Cyclotomic polynomial value Phi(10,n!).

Original entry on oeis.org

1, 1, 11, 1111, 318505, 205646281, 268365829681, 645113283892561, 2642842746670654081, 17340073528178593019521, 173401165343014841913811201, 2538767097801590027098850323201, 52643875748950481516906361827558401, 1503561738163266360299131304568093619201
Offset: 0

Views

Author

Robert Price, Aug 29 2015

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Cyclotomic[10, n!], {n, 0, 200}]

Formula

a(n) = A060884(n!) for n>0.

A326618 a(n) = n^18 + n^9 + 1.

Original entry on oeis.org

1, 3, 262657, 387440173, 68719738881, 3814699218751, 101559966746113, 1628413638264057, 18014398643699713, 150094635684419611, 1000000001000000001, 5559917315850179173, 26623333286045024257, 112455406962561892503, 426878854231297789441, 1477891880073843750001
Offset: 0

Views

Author

Richard N. Smith, Jul 15 2019

Keywords

Comments

a(n) = Phi_27(n) where Phi_k(x) is the k-th cyclotomic polynomial.

Crossrefs

Sequences of the type Phi_k(n), where Phi_k is the k-th cyclotomic polynomial: A000012 (k=0), A023443 (k=1), A000027 (k=2), A002061 (k=3), A002522 (k=4), A053699 (k=5), A002061 (k=6), A053716 (k=7), A002523 (k=8), A060883 (k=9), A060884 (k=10), A060885 (k=11), A060886 (k=12), A060887 (k=13), A060888 (k=14), A060889 (k=15), A060890 (k=16), A269442 (k=17), A060891 (k=18), A269446 (k=19), A060892 (k=20), A269483 (k=21), A269486 (k=22), A060893 (k=24), A269527 (k=25), A266229 (k=26), this sequence (k=27), A270204 (k=28), A060894 (k=30), A060895 (k=32), A060896 (k=36).
Cf. A153440 (indices of prime terms).

Programs

  • Magma
    [n^18+n^9+1: n in [0..17]]; // Vincenzo Librandi, Jul 15 2019
    
  • Mathematica
    Table[n^18 + n^9 + 1, {n, 0, 17}] (* Vincenzo Librandi, Jul 15 2019 *)
    Table[Cyclotomic[27, n], {n, 0, 17}]
  • PARI
    a(n) = polcyclo(27, n); \\ Michel Marcus, Jul 20 2019
Previous Showing 11-16 of 16 results.