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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A054880 a(n) = 3*(9^n - 1)/4.

Original entry on oeis.org

0, 6, 60, 546, 4920, 44286, 398580, 3587226, 32285040, 290565366, 2615088300, 23535794706, 211822152360, 1906399371246, 17157594341220, 154418349070986, 1389765141638880, 12507886274749926, 112570976472749340, 1013138788254744066, 9118249094292696600, 82064241848634269406, 738578176637708424660
Offset: 0

Views

Author

Paolo Dominici (pl.dm(AT)libero.it), May 23 2000

Keywords

Comments

Number of walks of length 2n+1 along the edges of a (3 dimensional) cube between two opposite vertices.
Urn A initially contains 3 labeled balls while urn B is empty. A ball is randomly selected and switched from one urn to the other. a(n)/3^(2n+1) is the probability that urn A is empty after 2n+1 switches. - Geoffrey Critzer, May 23 2013

Crossrefs

Programs

  • GAP
    List([0..30], n-> 3*(9^n -1)/4); # G. C. Greubel, Jul 14 2019
  • Magma
    [3*(9^n -1)/4: n in [0..30]]; // G. C. Greubel, Jul 14 2019
    
  • Mathematica
    Table[(2 n + 1)! Coefficient[Series[Sinh[x]^3, {x, 0, 2 n + 1}],
    x^(2 n + 1)], {n, 0, 30}]  (* Geoffrey Critzer, May 23 2013 *)
    LinearRecurrence[{10,-9},{0,6},30] (* Harvey P. Dale, Sep 17 2024 *)
  • PARI
    vector(30, n, n--; 3*(9^n -1)/4) \\ G. C. Greubel, Jul 14 2019
    
  • Sage
    [3*(9^n -1)/4 for n in (0..30)] # G. C. Greubel, Jul 14 2019
    

Formula

G.f.: (3/4)/(1 - 9*x) - (3/4)/(1 - x).
a(n) = 6*A002452(n).
sin(x)^3 = Sum_{k>=0} (-1)^(k+1)*a(k)*x^(2k+1)/(2k+1)!. - Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Apr 08 2001
a(n) = A015518(2n+1) - 1 = (A046717(2n+1) - 1)/2. - M. F. Hasler, Mar 20 2008
a(n) = 9*a(n-1) + 6 with n > 0, a(0) = 0. - Vincenzo Librandi, Aug 07 2010
a(n) = A066443(n) - 1. - Georg Fischer, Nov 25 2018
E.g.f.: 3*(exp(9*x) - exp(x))/4. - G. C. Greubel, Jul 14 2019
a(n) = 10*a(n-1) - 9*a(n-2) with a(0) = 0 and a(1) = 6. - Miquel A. Fiol, Mar 09 2024

A125857 Numbers whose base-9 representation is 22222222.......2.

Original entry on oeis.org

0, 2, 20, 182, 1640, 14762, 132860, 1195742, 10761680, 96855122, 871696100, 7845264902, 70607384120, 635466457082, 5719198113740, 51472783023662, 463255047212960, 4169295424916642, 37523658824249780, 337712929418248022
Offset: 1

Views

Author

Zerinvary Lajos, Feb 03 2007

Keywords

Comments

If f(1) := 1/x and f(n+1) = (f(n) + 2/f(n))/3, then f(n) = 3^(1-n) * (1/x + a(n)*x + O(x^3)). - Michael Somos, Jul 28 2020

Examples

			G.f. = 2*x^2 + 20*x^3 + 182*x^4 + 1640*x^5 + 14762*x^6 + 132860*x^7 + ... - _Michael Somos_, Jul 28 2020
		

Crossrefs

Cf. A002452.

Programs

  • Maple
    seq((9^n-1)*2/8, n=0..19);
  • Mathematica
    FromDigits[#, 9]&/@Table[PadRight[{2}, n, 2], {n, 0, 20}] (* Harvey P. Dale, Feb 02 2011 *)
    Table[(9^(n - 1) - 1)*2/8, {n, 20}] (* Wesley Ivan Hurt, Mar 29 2014 *)
  • PARI
    Vec(2*x^2/((x-1)*(9*x-1)) + O(x^100)) \\ Colin Barker, Sep 30 2014
    
  • PARI
    {a(n) = (9^(n-1) - 1)/4}; /* Michael Somos, Jul 02 2017 */

Formula

a(n) = (9^(n-1) - 1)*2/8.
a(n) = 9*a(n-1) + 2 (with a(1)=0). - Vincenzo Librandi, Sep 30 2010
a(n) = 2 * A002452(n). - Vladimir Pletser, Mar 29 2014
From Colin Barker, Sep 30 2014: (Start)
a(n) = 10*a(n-1) - 9*a(n-2).
G.f.: 2*x^2 / ((x-1)*(9*x-1)). (End)
a(n) = -a(2-n) * 9^(n-1) for all n in Z. - Michael Somos, Jul 02 2017
a(n) = A191681(n-1)/2. - Klaus Purath, Jul 03 2020

A210461 Cipolla pseudoprimes to base 3: (9^p-1)/8 for any odd prime p.

Original entry on oeis.org

91, 7381, 597871, 3922632451, 317733228541, 2084647712458321, 168856464709124011, 1107867264956562636991, 588766087155780604365200461, 47690053059618228953581237351, 25344449488056571213320166359119221, 166284933091139163730593611482181209801
Offset: 1

Views

Author

Bruno Berselli, Jan 22 2013 - proposed by Umberto Cerruti (Department of Mathematics "Giuseppe Peano", University of Turin, Italy)

Keywords

Comments

This is the case a=3 of Theorem 1 in the paper of Hamahata and Kokubun (see Links section).

Examples

			91 is in the sequence because 91=((3^3-1)/2)*((3^3+1)/4), even if p=3 divides 3*(3^2-1), and 3^90 = (91*8+1)^15 == 1 (mod 91).
7381 is in the sequence because 7381=((3^5-1)/2)*((3^5+1)/4) and 3^7380 = (7381*472400+1)^369 == 1 (mod 7381).
		

References

  • Michele Cipolla, Sui numeri composti P che verificano la congruenza di Fermat a^(P-1) = 1 (mod P), Annali di Matematica 9 (1904), p. 139-160.

Crossrefs

Programs

  • Haskell
    a210461 = (`div` 8) . (subtract 1) . (9 ^) . a065091
    -- Reinhard Zumkeller, Jan 22 2013
  • Magma
    [(9^NthPrime(n)-1)/8: n in [2..12]];
    
  • Maple
    P:=proc(q)local n;
    for n from 2 to q do print((9^ithprime(n)-1)/8);
    od; end: P(100); # Paolo P. Lava, Oct 11 2013
  • Mathematica
    (9^# - 1)/8 & /@ Prime[Range[2, 12]]
  • Maxima
    Prime(n) := block(if n = 1 then return(2), return(next_prime(Prime(n-1))))$
    makelist((9^Prime(n)-1)/8, n, 2, 12);
    

A218728 a(n) = (25^n - 1)/24.

Original entry on oeis.org

0, 1, 26, 651, 16276, 406901, 10172526, 254313151, 6357828776, 158945719401, 3973642985026, 99341074625651, 2483526865641276, 62088171641031901, 1552204291025797526, 38805107275644938151, 970127681891123453776, 24253192047278086344401, 606329801181952158610026
Offset: 0

Views

Author

M. F. Hasler, Nov 04 2012

Keywords

Comments

Partial sums of powers of 25 (A009969); q-integers for q=25.
Partial sums are in A014914. Also, the sequence is related to A014943 by A014943(n) = n*a(n) - Sum_{i=0..n-1} a(i) for n > 0. - Bruno Berselli, Nov 07 2012

Crossrefs

Programs

Formula

a(n) = floor(25^n/24).
From Vincenzo Librandi, Nov 07 2012: (Start)
G.f.: x/((1-x)*(1-25*x)).
a(n) = 26*a(n-1) - 25*a(n-2). (End)
E.g.f.: exp(13*x)*sinh(12*x)/12. - Elmo R. Oliveira, Aug 27 2024
a(n) = 25*a(n-1) + 1. - Jerzy R Borysowicz, Sep 05 2025

A218743 a(n) = (40^n - 1)/39.

Original entry on oeis.org

0, 1, 41, 1641, 65641, 2625641, 105025641, 4201025641, 168041025641, 6721641025641, 268865641025641, 10754625641025641, 430185025641025641, 17207401025641025641, 688296041025641025641, 27531841641025641025641, 1101273665641025641025641, 44050946625641025641025641
Offset: 0

Views

Author

M. F. Hasler, Nov 04 2012

Keywords

Comments

Partial sums of powers of 40 (A009983).

Crossrefs

Programs

  • Magma
    [n le 2 select n-1 else 41*Self(n-1) - 40*Self(n-2): n in [1..20]]; // Vincenzo Librandi, Nov 07 2012
  • Mathematica
    LinearRecurrence[{41, -40}, {0, 1}, 30] (* Vincenzo Librandi, Nov 07 2012 *)
  • Maxima
    A218743(n):=floor(40^n/39)$ makelist(A218743(n),n,0,30); /* Martin Ettl, Nov 05 2012 */
    
  • PARI
    a(n)=40^n\39
    

Formula

a(n) = floor(40^n/39).
From Vincenzo Librandi, Nov 07 2012: (Start)
G.f.: x/((1-x)*(1-40*x)).
a(n) = 41*a(n-1) - 40*a(n-2). (End)
E.g.f.: exp(x)*(exp(39*x) - 1)/39. - Elmo R. Oliveira, Aug 29 2024

A269025 a(n) = Sum_{k = 0..n} 60^k.

Original entry on oeis.org

1, 61, 3661, 219661, 13179661, 790779661, 47446779661, 2846806779661, 170808406779661, 10248504406779661, 614910264406779661, 36894615864406779661, 2213676951864406779661, 132820617111864406779661, 7969237026711864406779661, 478154221602711864406779661
Offset: 0

Views

Author

Ilya Gutkovskiy, Feb 18 2016

Keywords

Comments

Partial sums of powers of 60 (A159991).
Converges in a 10-adic sense to ...762711864406779661.
More generally, the ordinary generating function for the Sum_{k = 0..n} m^k is 1/((1 - m*x)*(1 - x)). Also, Sum_{k = 0..n} m^k = (m^(n + 1) - 1)/(m - 1).

Crossrefs

Cf. A159991.
Cf. similar sequences of the form (k^n-1)/(k-1): A000225 (k=2), A003462 (k=3), A002450 (k=4), A003463 (k=5), A003464 (k=6), A023000 (k=7), A023001 (k=8), A002452 (k=9), A002275 (k=10), A016123 (k=11), A016125 (k=12), A091030 (k=13), A135519 (k=14), A135518 (k=15), A131865 (k=16), A091045 (k=17), A218721 (k=18), A218722 (k=19), A064108 (k=20), A218724-A218734 (k=21..31), A132469 (k=32), A218736-A218753 (k=33..50), this sequence (k=60), A133853 (k=64), A094028 (k=100), A218723 (k=256), A261544 (k=1000).

Programs

  • Mathematica
    Table[Sum[60^k, {k, 0, n}], {n, 0, 15}]
    Table[(60^(n + 1) - 1)/59, {n, 0, 15}]
    LinearRecurrence[{61, -60}, {1, 61}, 15]
  • PARI
    a(n)=60^n + 60^n\59 \\ Charles R Greathouse IV, Jul 26 2016

Formula

G.f.: 1/((1 - 60*x)*(1 - x)).
a(n) = (60^(n + 1) - 1)/59 = 60^n + floor(60^n/59).
a(n+1) = 60*a(n) + 1, a(0)=1.
a(n) = Sum_{k = 0..n} A159991(k).
Sum_{n>=0} 1/a(n) = 1.016671221665660580331...
E.g.f.: exp(x)*(60*exp(59*x) - 1)/59. - Stefano Spezia, Mar 23 2023

A291560 E.g.f. A(x,k) satisfies: sin(A(x,k)) = k * sin(x).

Original entry on oeis.org

1, -1, 1, 1, -10, 9, -1, 91, -315, 225, 1, -820, 8694, -18900, 11025, -1, 7381, -224730, 1143450, -1819125, 893025, 1, -66430, 5684679, -61647300, 203378175, -255405150, 108056025, -1, 597871, -142714845, 3162834675, -19494349875, 47377655325, -49165491375, 18261468225, 1, -5380840, 3573251964, -158546770200, 1734021238950, -7311738634200, 14041664336700, -12417798393000, 4108830350625, -1, 48427561, -89379726660, 7858123038900, -148224512094750, 1025176095093150, -3257761647640500, 5167045911327300, -3981456609755625, 1187451971330625
Offset: 1

Views

Author

Paul D. Hanna, Aug 26 2017

Keywords

Comments

Compare to the law of sines of a spherical triangle: sin(A)/sin(a) = k.
The series reversion of e.g.f. A(x,k) wrt x equals A(x, 1/k).

Examples

			This triangle of coefficients T(n,r) in e.g.f. A(x,k) begins:
[1],
[-1, 1],
[1, -10, 9],
[-1, 91, -315, 225],
[1, -820, 8694, -18900, 11025],
[-1, 7381, -224730, 1143450, -1819125, 893025],
[1, -66430, 5684679, -61647300, 203378175, -255405150, 108056025],
[-1, 597871, -142714845, 3162834675, -19494349875, 47377655325, -49165491375, 18261468225],
[1, -5380840, 3573251964, -158546770200, 1734021238950, -7311738634200, 14041664336700, -12417798393000, 4108830350625],
[-1, 48427561, -89379726660, 7858123038900, -148224512094750, 1025176095093150, -3257761647640500, 5167045911327300, -3981456609755625, 1187451971330625],
[1, -435848050, 2234929014549, -387282522072600, 12391233508580850, -136052492985945900, 674608025957515650, -1713147048499887000, 2313226290268018125, -1579311121869731250, 428670161650355625], ...
where e.g.f. A(x,k) = Sum_{n>=1, r=1..n} T(n,r) * x^(2*n-1) * k^(2*r-1) / (2*n-1)!.
E.g.f.: A(x,k) = k*x + (k^3 - k)*x^3/3! + (9*k^5 - 10*k^3 + k)*x^5/5! + (225*k^7 - 315*k^5 + 91*k^3 - k)*x^7/7! + (11025*k^9 - 18900*k^7 + 8694*k^5 - 820*k^3 + k)*x^9/9! + (893025*k^11 - 1819125*k^9 + 1143450*k^7 - 224730*k^5 + 7381*k^3 - k)*x^11/11! + (108056025*k^13 - 255405150*k^11 + 203378175*k^9 - 61647300*k^7 + 5684679*k^5 - 66430*k^3 + k)*x^13/13! + (18261468225*k^15 - 49165491375*k^13 + 47377655325*k^11 - 19494349875*k^9 + 3162834675*k^7 - 142714845*k^5 + 597871*k^3 - k)*x^15/15! + (4108830350625*k^17 - 12417798393000*k^15 + 14041664336700*k^13 - 7311738634200*k^11 + 1734021238950*k^9 - 158546770200*k^7 + 3573251964*k^5 - 5380840*k^3 + k)*x^17/17! + (1187451971330625*k^19 - 3981456609755625*k^17 + 5167045911327300*k^15 - 3257761647640500*k^13 + 1025176095093150*k^11 - 148224512094750*k^9 + 7858123038900*k^7 - 89379726660*k^5 + 48427561*k^3 - k)*x^19/19! +...
such that sin(A(x,k)) = k * sin(x).
		

Crossrefs

Cf. A002452 (column 1), A001818 (diagonal), A291561 (diagonal), A291562 (central terms).
Cf. A291527 (variant).

Programs

  • Mathematica
    T[n_, k_] := If[ n < 1, 0, (2 n - 1)! Coefficient[ SeriesCoefficient[ ArcSin[y Sin[x]], {x, 0, 2 n - 1}], y, 2 k - 1]]; (* Michael Somos, Jul 03 2018 *)
    T[n_, k_] := ((-1)^n/((2*k - 1)^2*4^(2*k - 1)))*((2*k)!/k!)^2 * Sum[((-1)^i*(2*i - 1)^(2*n - 1))/((k - i)!*(k + i - 1)!), {i, 1, n}]; (* Vjekoslav-Leonard Prcic, Oct 10 2018 *)
  • PARI
    {T(n, r) = (2*n-1)! * polcoeff( polcoeff( asin( k*sin(x + O(x^(2*n)))), 2*n-1,x), 2*r-1, k)}
    for(n=1, 10, for(r=1, n, print1(T(n, r), ", ")); print(""))

Formula

E.g.f. A(x,k) = Sum_{n>=1, r=1..n} T(n,r) * x^(2*n-1) * k^(2*r-1)/(2*n-1)!, satisfies:
(1) sin(A(x,k)) = k * sin(x).
(2) A(x,k) = asin(k * sin(x)).
(3) A( A(x,k), 1/k) = x.
(4) sin( A^r(x,k) ) = k^r * sin(x) where A^r(x,k) = A(x,k^r) is the r-th iteration of A(x,k) wrt x, with A^0(x,k) = x.
(5) A(x,1) = x.
Row sums of n-th row equals zero for n>1.
T(n+1,1) = (-1)^n for n>=0.
T(n+1,2) = (-1)^(n-1) * (9^n - 1)/8 for n>=1.
T(n+1,n+1) = ( (2*n)! / (n!*2^n) )^2 = A001818(n) for n>=0.
T(n, r) = (-1)^n / ((2*r - 1)^2 * 4^(2*r - 1)) * ((2*r)! / r!)^2 * Sum_{i=1..n} (-1)^i * (2*i - 1)^(2*n - 1) / ((r - i)! * (r + i - 1)!). - Vjekoslav-Leonard Prcic, Oct 10 2018

A218725 a(n) = (22^n - 1)/21.

Original entry on oeis.org

0, 1, 23, 507, 11155, 245411, 5399043, 118778947, 2613136835, 57489010371, 1264758228163, 27824681019587, 612142982430915, 13467145613480131, 296277203496562883, 6518098476924383427, 143398166492336435395, 3154759662831401578691, 69404712582290834731203
Offset: 0

Views

Author

M. F. Hasler, Nov 04 2012

Keywords

Comments

Partial sums of powers of 22; q-integers for q=22: Diagonal k=1 in the triangle A022186.
Partial sums are in A014907. Also, the sequence is related to A014940 by A014940(n) = n*a(n) - Sum_{i=0..n-1} a(i) for n > 0. [Bruno Berselli, Nov 06 2012]

Crossrefs

Programs

Formula

a(n) = floor(22^n/21).
G.f.: x/((1-x)*(1-22*x)). [Bruno Berselli, Nov 06 2012]
a(n) = 23*a(n-1) - 22*a(n-2). - Vincenzo Librandi, Nov 07 2012
E.g.f.: exp(x)*(exp(21*x) - 1)/21. - Elmo R. Oliveira, Aug 29 2024

A218737 a(n) = (34^n - 1)/33.

Original entry on oeis.org

0, 1, 35, 1191, 40495, 1376831, 46812255, 1591616671, 54114966815, 1839908871711, 62556901638175, 2126934655697951, 72315778293730335, 2458736461986831391, 83597039707552267295, 2842299350056777088031, 96638177901930420993055, 3285698048665634313763871
Offset: 0

Views

Author

M. F. Hasler, Nov 04 2012

Keywords

Comments

Partial sums of powers of 34 (A009978).

Crossrefs

Programs

Formula

From Vincenzo Librandi, Nov 07 2012: (Start)
G.f.: x/((1 - x)*(1 - 34*x)).
a(n) = 35*a(n-1) - 34*a(n-2).
a(n) = floor(34^n/33). (End)
E.g.f.: exp(x)*(exp(33*x) - 1)/33. - Stefano Spezia, Mar 26 2023

A218738 a(n) = (35^n - 1)/34.

Original entry on oeis.org

0, 1, 36, 1261, 44136, 1544761, 54066636, 1892332261, 66231629136, 2318107019761, 81133745691636, 2839681099207261, 99388838472254136, 3478609346528894761, 121751327128511316636, 4261296449497896082261, 149145375732426362879136, 5220088150634922700769761
Offset: 0

Views

Author

M. F. Hasler, Nov 04 2012

Keywords

Comments

Partial sums of powers of 35 (A009979).

Crossrefs

Programs

Formula

From Vincenzo Librandi, Nov 07 2012: (Start)
G.f.: x/((1 - x)*(1 - 35*x)).
a(n) = 36*a(n-1) - 35*a(n-2).
a(n) = floor(35^n/34). (End)
E.g.f.: exp(x)*(exp(34*x) - 1)/34. - Stefano Spezia, Mar 28 2023
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