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 1-4 of 4 results.

A305862 a(n) = 384*4^n - 576*3^n + 220*2^n - 14.

Original entry on oeis.org

14, 234, 1826, 10770, 55154, 260274, 1167026, 5059890, 21442994, 89438514, 368866226, 1509026610, 6137242034, 24853275954, 100327829426, 404059098930, 1624486948274, 6522713868594, 26165182536626, 104883769004850, 420204307937714, 1682825158192434, 6737324873467826
Offset: 0

Views

Author

Vincenzo Librandi, Jun 15 2018

Keywords

Comments

From Bruno Berselli, Jun 15 2018: (Start)
a(0) = 2*7 and a(40) = 2*232110255958477539427146457 are semiprimes. For which values of n > 40 is a(n) semiprime?
For odd n, a(n) is divisible by 2*3.
For n == 3 (mod 4), a(n) is divisible by 2*3*5.
For n == 0 or 5 (mod 6), a(n) is divisible by 2*7.
For n == 2 or 4 (mod 5), a(n) is divisible by 2*11.
For n == 1 or 11 (mod 12), a(n) is divisible by 2*3*13.
For n == 15 (mod 16), a(n) is divisible by 2*3*5*17^2, etc.
If a(n) is divisible by 37 then it is also divisible by 3*5*7*13*19*73. (End)

Crossrefs

Programs

  • Magma
    [384*4^n-576*3^n+220*2^n-14: n in [0..30]];
    
  • Mathematica
    Table[384 4^n - 576 3^n + 220 2^n - 14, {n, 0, 30}]
  • PARI
    a(n) = 384*4^n - 576*3^n + 220*2^n - 14; \\ Michel Marcus, Jul 03 2018

Formula

G.f.: 2*(7 + 47*x - 12*x^2)/((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)).
a(n) = 10*a(n-1) - 35*a(n-2) + 50*a(n-3) - 24*a(n-4).
a(n) = 14*A000453(n+4) + 94*A000453(n+3) - 24*A000453(n+2) for n>1. - Bruno Berselli, Jun 15 2018

A305863 a(n) = 6144*5^n - 12288*4^n + 7616*3^n - 1472*2^n + 41.

Original entry on oeis.org

41, 1513, 19689, 175465, 1287657, 8420713, 51126249, 295141225, 1644285417, 8927926633, 47563308009, 249806529385, 1297882995177, 6687496584553, 34237868091369, 174415093507945, 885051189224937, 4477377106010473, 22596025278436329, 113818651291052905
Offset: 0

Views

Author

Vincenzo Librandi, Jul 04 2018

Keywords

Crossrefs

Programs

  • Magma
    [6144*5^n-12288*4^n+7616*3^n-1472*2^n+41: n in [0..20]];
  • Mathematica
    Table[6144 5^n - 12288 4^n + 7616 3^n - 1472 2^n + 41, {n, 0, 30}]

Formula

G.f.: (41 + 898*x + 479*x^2 - 490*x^3 + 56*x^4)/((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)*(1 - 5*x)).
a(n) = 15*a(n-1) - 85*a(n-2) + 225*a(n-3) - 274*a(n-4) + 120*a(n-5) for n>5.

A316526 a(n) = 122880*6^n - 307200*5^n + 264960*4^n - 90240*3^n + 9844*2^n - 122.

Original entry on oeis.org

122, 9966, 210134, 2741670, 27930182, 245220486, 1953210374, 14543545350, 103166087942, 706033804806, 4702595902214, 30675859444230, 196880387684102, 1247535454225926, 7825081688699654, 48684535015586310, 300917096071974662, 1850113238390115846
Offset: 0

Views

Author

Vincenzo Librandi, Jul 06 2018

Keywords

Crossrefs

Programs

  • Magma
    [122880*6^n-307200*5^n+264960*4^n-90240*3^n+9844*2^n-122: n in [0..20]];
  • Mathematica
    Table[122880 6^n - 307200 5^n + 264960 4^n - 90240 3^n + 9844 2^n - 122, {n, 0, 20}]

Formula

G.f.: 2*(61 + 3702*x + 11099*x^2 - 8382*x^3 + 840*x^4)/((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)*(1 - 5*x)*(1 - 6*x)).
a(n) = 21*a(n-1) - 175*a(n-2) + 735*a(n-3) - 1624*a(n-4) + 1764*a(n-5) - 720*a(n-6) for n>6.

A345394 Array read by ascending antidiagonals: A(n, k) = n!*[x^n] Li(-k, 1 - exp(-4*x))/(4*sinh(x)), where Li(n, z) is the polylogarithm function.

Original entry on oeis.org

1, 2, 1, 5, 6, 1, 14, 37, 14, 1, 41, 234, 165, 30, 1, 122, 1513, 1826, 613, 62, 1, 365, 9966, 19689, 10770, 2085, 126, 1, 1094, 66637, 210134, 175465, 55154, 6757, 254, 1, 3281, 450834, 2236365, 2741670, 1287657, 260274, 21285, 510, 1, 9842, 3077713, 23819306, 41809933, 27930182, 8420713, 1167026, 65893, 1022, 1
Offset: 0

Views

Author

Stefano Spezia, Jun 17 2021

Keywords

Examples

			n\k|   0     1      2       3        4 ...
---+----------------------------------
0  |   1     1      1       1        1 ...
1  |   2     6     14      30       62 ...
2  |   5    37    165     613     2085 ...
3  |  14   234   1826   10770    55154 ...
4  |  41  1513  19689  175465  1287657 ...
...
		

Crossrefs

Cf. A000012 (n = 0), A007051 (k = 0), A081188 (k = 1), A305861 (n = 2), A305862 (n = 3), A305863 (n = 4), A316526 (n = 5), A345393.

Programs

  • Mathematica
    A[n_,k_]:=n!Coefficient[Series[PolyLog[-k,1-Exp[-4t]]/(4Sinh[t]),{t,0,n}],t,n]; Flatten[Table[A[n-k,k],{n,0,9},{k,0,n}]]
Showing 1-4 of 4 results.