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.

Previous Showing 11-16 of 16 results.

A021040 Decimal expansion of 1/36.

Original entry on oeis.org

0, 2, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7
Offset: 0

Views

Author

Keywords

Examples

			0.0277777777777777777777777777777777777777777777777777777777777777777777777777...
		

Crossrefs

Cf. A010727.

Programs

  • Mathematica
    Join[{0},RealDigits[1/36,10,120][[1]]] (* or *) PadRight[{0,2},120,{7}] (* Harvey P. Dale, Jul 14 2017 *)
  • PARI
    1./36

A321358 a(n) = (2*4^n + 7)/3.

Original entry on oeis.org

3, 5, 13, 45, 173, 685, 2733, 10925, 43693, 174765, 699053, 2796205, 11184813, 44739245, 178956973, 715827885, 2863311533, 11453246125, 45812984493, 183251937965, 733007751853, 2932031007405, 11728124029613, 46912496118445, 187649984473773, 750599937895085, 3002399751580333
Offset: 0

Views

Author

Paul Curtz, Nov 07 2018

Keywords

Comments

Difference table:
3, 5, 13, 45, 173, 685, 2733, ... (this sequence)
2, 8, 32, 128, 512, 2048, 8192, ... A004171
6, 24, 96, 384, 1536, 6144, 24576, ... A002023

Crossrefs

Programs

  • Mathematica
    a[n_]:= (2*4^n + 7)/3; Array[a, 20, 0] (* or *)
    CoefficientList[Series[1/3 (7 E^x + 2 E^(4 x)), {x, 0, 20}], x]*Table[n!, {n, 0, 20}] (* Stefano Spezia, Nov 10 2018 *)
  • PARI
    a(n) = (2*4^n + 7)/3; \\ Michel Marcus, Nov 08 2018
    
  • PARI
    Vec((3 - 10*x) / ((1 - x)*(1 - 4*x)) + O(x^30)) \\ Colin Barker, Nov 10 2018

Formula

O.g.f.: (3 - 10*x) / ((1 - x)*(1 - 4*x)). - Colin Barker, Nov 10 2018
E.g.f.: (1/3)*(7*exp(x) + 2*exp(4*x)). - Stefano Spezia, Nov 10 2018
a(n) = 5*a(n-1) - 4*a(n-2), a(0) = 3, a(1) = 5.
a(n) = 4*a(n-1) - 7, a(0) = 3.
a(n) = (2/3)*(4^n-1)/3 + 3.
a(n) = A171382(2*n) = A155980(2*n+2).
a(n) = A193579(n)/3.
a(n) = A007583(n) + 2 = A001045(2*n+1) + 2.

Extensions

More terms from Michel Marcus, Nov 08 2018

A321421 a(n) = 10*(4^n - 1)/3 + 1.

Original entry on oeis.org

1, 11, 51, 211, 851, 3411, 13651, 54611, 218451, 873811, 3495251, 13981011, 55924051, 223696211, 894784851, 3579139411, 14316557651, 57266230611, 229064922451, 916259689811, 3665038759251, 14660155037011, 58640620148051, 234562480592211, 938249922368851
Offset: 0

Views

Author

Paul Curtz, Nov 09 2018

Keywords

Crossrefs

Programs

  • GAP
    List([0..25],n->10*(4^n-1)/3+1); # Muniru A Asiru, Nov 10 2018
  • Maple
    seq(coeff(series((1+6*x)/((1-x)*(1-4*x)),x,n+1), x, n), n = 0 .. 25); # Muniru A Asiru, Nov 10 2018
  • Mathematica
    a[n_]:=10*(4^n - 1)/3 + 1 ; Array[a, 20, 0] (* or *)
    CoefficientList[Series[-((7 E^x)/3) + (10 E^(4 x))/3 , {x, 0, 20}], x]*Table[n!, {n, 0, 20}] (* Stefano Spezia, Nov 10 2018 *)
    LinearRecurrence[{5,-4},{1,11},30] (* Harvey P. Dale, Aug 22 2020 *)
  • PARI
    Vec((1 + 6*x) / ((1 - x)*(1 - 4*x)) + O(x^30)) \\ Colin Barker, Nov 10 2018
    

Formula

a(n) = 4*a(n-1) + 7, a(0) = 1 for n > 0.
a(n) = 5*a(n-1) - 4*a(n-2), a(0) = 1, a(1) = 11, n > 1.
a(n) = a(n-1) + 10*4^(n-1), a(0) = 1, n > 0.
a(n) = A086462(n) + 1 for n > 0. - Michel Marcus, Nov 09 2018
G.f.: (1 + 6*x) / ((1 - x)*(1 - 4*x)). - Colin Barker, Nov 10 2018
E.g.f.: (-7*exp(x) + 10*exp(4*x))/3. - Stefano Spezia, Nov 10 2018
a(n) = 10*A002450(n) + 1. - Omar E. Pol, Nov 10 2018

Extensions

More terms from Colin Barker, Nov 10 2018

A044567 Numbers n such that string 6,6 occurs in the base 7 representation of n but not of n+1.

Original entry on oeis.org

48, 97, 146, 195, 244, 293, 342, 391, 440, 489, 538, 587, 636, 685, 734, 783, 832, 881, 930, 979, 1028, 1077, 1126, 1175, 1224, 1273, 1322, 1371, 1420, 1469, 1518, 1567, 1616, 1665, 1714, 1763, 1812, 1861, 1910, 1959, 2008, 2057, 2106, 2155, 2204, 2253, 2302
Offset: 1

Views

Author

Keywords

Crossrefs

Cf. A157362, A010727 [From Vincenzo Librandi, Mar 12 2009]

Programs

  • Mathematica
    SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{6,6}]>0,1,0],{n,2500}],{1,0}][[All,1]] (* Harvey P. Dale, Aug 20 2021 *)

Extensions

Incorrect Mathematica program deleted by Harvey P. Dale, Aug 20 2021

A253671 a(n) = floor(A000111(n)/A000111(n-1)).

Original entry on oeis.org

1, 1, 2, 2, 3, 3, 4, 5, 5, 6, 7, 7, 8, 8, 9, 10, 10, 11, 12, 12, 13, 14, 14, 15, 15, 16, 17, 17, 18, 19, 19, 20, 21, 21, 22, 22, 23, 24, 24, 25, 26, 26, 27, 28, 28, 29, 29, 30, 31, 31, 32, 33, 33, 34, 35, 35, 36, 36, 37, 38, 38, 39, 40, 40
Offset: 1

Views

Author

Paul Curtz, Jan 08 2015, with the help of Jean-François Alcover

Keywords

Comments

1, 2, 3, 4, ... first appear at n = 1, 3, 5, 7, 8, 10, 11, 13, ... . a(500) = 318.
Numbers appearing only once: interleave 4+7*n, 6+7*n, 9+7*n = 4, 6, 9, 11, 13, 16, ... .
This is a nondecreasing sequence.
The ratio a(n)/n asymptotically tends to 7/11 = 0.6363... - Jean-François Alcover, Jul 21 2015

Examples

			Floor of 1/1, 1/1, 2/1, 5/2, 16/5, 61/16, ... .
1=1*1+0, 1=1*1+0, 2=2*1+0, 5=2*2+1, 16=3*5+1, 61=3*16+13, 272=4*61+28, ... .
		

Crossrefs

Programs

  • Mathematica
    max = 500; ee = Table[2^n*EulerE[n, 1] + EulerE[n] - 1, {n, 0, max}]; A000111 = Table[Differences[ee, n] // First // Abs, {n, 0, max}]; Table[Quotient[A000111[[n + 1]], A000111[[n]]], {n, 1, max}] (* Jean-François Alcover, Jan 08 2015 *)
  • PARI
    Vec(x*(x^14-x^13+x^12-x^11+x^10+x^9+x^7+x^6+x^4+x^2+1)/((x-1)^2*(x^10+x^9+x^8+x^7+x^6+x^5+x^4+x^3+x^2+x+1)) + O(x^100)) \\ Colin Barker, Jan 22 2015
    
  • Python
    # requires python 3.2 or higher
    from itertools import accumulate
    A253671_list, blist, l1, l2 = [1], [1], 1, 1
    for n in range(10**2):
        blist = list(reversed(list(accumulate(reversed(blist))))) + [0] if n % 2 else [0]+list(accumulate(blist))
        l2, l1 = l1, sum(blist)
        A253671_list.append(l1//l2) # Chai Wah Wu, Jan 29 2015

Formula

a(n+2) = a(n+1) + (0, 1, 0, followed by a sequence of period 11: repeat 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1).
a(n+12) = a(n+1) + (6, 7, 6, followed by 7's = A010727).
a(n) = a(n-1) + a(n-11) - a(n-12) for n>15. - Colin Barker, Jan 22 2015
G.f.: x*(x^14-x^13+x^12-x^11+x^10+x^9+x^7+x^6+x^4+x^2+1) / ((x-1)^2*(x^10+x^9+x^8+x^7+x^6+x^5+x^4+x^3+x^2+x+1)). - Colin Barker, Jan 22 2015

A255910 Decimal expansion of 16/9.

Original entry on oeis.org

1, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7
Offset: 1

Views

Author

Derek Orr, Mar 10 2015

Keywords

Comments

Cutting the unit square [0,1] x [0,1] into two equal areas with a parabolic curve y = A*x^2 requires A to be 16/9. If you extend this to an arbitrary square [0,s] x [0,s], A = (16/9)*s.
Except for the first terms, identical to A186684, A021040 and A010727.

Examples

			1.7777777777777777777777777777...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[16/9, 10, 100][[1]] (* Vincenzo Librandi, Mar 24 2015 *)
  • PARI
    x=16/9; for(n=1, 100, d=floor(x); x=(x-d)*10; print1(d,", "))

Formula

From Elmo R. Oliveira, Aug 05 2024: (Start)
G.f.: x + 7*x^2/(1 - x).
E.g.f.: 7*(exp(x) - 1) - 6*x.
a(n) = 7 - 6*0^(n-1).
a(n) = 7, n > 1. (End)
Previous Showing 11-16 of 16 results.