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.

A104891 a(0) = 0; a(n) = 5*a(n-1) + 5.

Original entry on oeis.org

0, 5, 30, 155, 780, 3905, 19530, 97655, 488280, 2441405, 12207030, 61035155, 305175780, 1525878905, 7629394530, 38146972655, 190734863280, 953674316405, 4768371582030, 23841857910155, 119209289550780, 596046447753905, 2980232238769530, 14901161193847655
Offset: 0

Views

Author

Alexandre Wajnberg, Apr 24 2005

Keywords

Comments

Number of integers from 0 to (10^n)-1 that lack 0, 1, 2, 3 and 4 as a digit.
Number of monic irreducible polynomials of degree 1 in GF(5)[x1,...,xn]. - Max Alekseyev, Jan 23 2006

Examples

			a(3) = 5*a(2) + 5 = 5*30 + 5 = 155.
		

Crossrefs

Programs

  • Magma
    [5*(5^n -1)/4: n in [0..30]]; // G. C. Greubel, Jun 15 2021
    
  • Maple
    a:=n->add(5^j,j=1..n): seq(a(n),n=0..30); # Zerinvary Lajos, Jun 27 2007
  • Mathematica
    RecurrenceTable[{a[n]==5*a[n-1]+5, a[0]==0}, a, {n, 0, 30}] (* Vaclav Kotesovec, Jul 25 2014 *)
    NestList[5#+5&,0,30] (* Harvey P. Dale, Oct 04 2019 *)
  • PARI
    concat(0, Vec(5*x/((x-1)*(5*x-1)) + O(x^30))) \\ Colin Barker, Jul 25 2014
    
  • Sage
    [5*(5^n -1)/4 for n in (0..30)] # G. C. Greubel, Jun 15 2021

Formula

a(n) = 5*(5^n - 1)/4. - Max Alekseyev, Jan 23 2006
a(n) = a(n-1) + 5^n with a(0)=0. - Vincenzo Librandi, Nov 13 2010
From Colin Barker, Jul 25 2014: (Start)
a(n) = 6*a(n-1) - 5*a(n-2).
G.f.: 5*x / ((1-x)*(1-5*x)). (End)
E.g.f.: (5/4)*(exp(5*x) - exp(x)). - G. C. Greubel, Jun 15 2021

A104896 a(0) = 0; a(n) = 7*a(n-1) + 7.

Original entry on oeis.org

0, 7, 56, 399, 2800, 19607, 137256, 960799, 6725600, 47079207, 329554456, 2306881199, 16148168400, 113037178807, 791260251656, 5538821761599, 38771752331200, 271402266318407, 1899815864228856, 13298711049601999, 93090977347214000, 651636841430498007
Offset: 0

Views

Author

Alexandre Wajnberg, Apr 24 2005

Keywords

Comments

Conjecture: this is also the number of integers from 0 to 10^n - 1 that lack 0, 1 and 2 as a digit.
Number of monic irreducible polynomials of degree 1 in GF(7)[x1,...,xn]. - Max Alekseyev, Jan 23 2006

Crossrefs

Programs

  • Magma
    [(7/6)*(7^n -1): n in [0..30]]; // G. C. Greubel, Jun 09 2021
    
  • Maple
    a:=n->sum (7^j,j=1..n): seq(a(n), n=0..30); # Zerinvary Lajos, Oct 03 2007
  • Mathematica
    RecurrenceTable[{a[n]==7*a[n-1]+7,a[0]==0},a,{n,0,30}] (* Vaclav Kotesovec, Jul 25 2014 *)
  • PARI
    concat(0, Vec(7*x/((x-1)*(7*x-1)) + O(x^30))) \\ Colin Barker, Jul 25 2014
    
  • Sage
    [(7/6)*(7^n -1) for n in (0..30)] # G. C. Greubel, Jun 09 2021

Formula

a(n) = (7^(n+1) - 7) / 6. - Max Alekseyev, Jan 23 2006
a(n) = a(n-1) + 7^n with a(0)=0. - Vincenzo Librandi, Nov 13 2010
From Colin Barker, Jul 25 2014: (Start)
a(n) = 8*a(n-1) - 7*a(n-2).
G.f.: 7*x / ((x-1)*(7*x-1)). (End)
E.g.f.: (7/6)*(exp(7*x) - exp(x)). - G. C. Greubel, Jun 09 2021

A105281 a(0)=0; a(n) = 6*a(n-1) + 6.

Original entry on oeis.org

0, 6, 42, 258, 1554, 9330, 55986, 335922, 2015538, 12093234, 72559410, 435356466, 2612138802, 15672832818, 94036996914, 564221981490, 3385331888946, 20311991333682, 121871948002098, 731231688012594, 4387390128075570, 26324340768453426, 157946044610720562
Offset: 0

Views

Author

Alexandre Wajnberg, Apr 25 2005

Keywords

Comments

Number of integers from 0 to (10^n) - 1 that lack 0, 1, 2 and 3 as a digit.
a(n) is the expected number of tosses of a single die needed to obtain for the first time a string of n consecutive 6's. - Jean M. Morales, Aug 04 2012

Crossrefs

Programs

  • Maple
    a:=n->add(6^j,j=1..n): seq(a(n),n=0..30); # Zerinvary Lajos, Oct 03 2007
  • Mathematica
    NestList[6#+6&,0,30] (* Harvey P. Dale, Jul 24 2012 *)
  • PARI
    a(n)=if(n<0,0, (6^n-1)*6/5)

Formula

a(n) = 6^n + a(n-1) (with a(0)=0). - Vincenzo Librandi, Nov 13 2010
From Colin Barker, Jan 28 2013: (Start)
a(n) = 7*a(n-1) - 6*a(n-2).
G.f.: 6*x/((x-1)*(6*x-1)). (End)
From Elmo R. Oliveira, Mar 16 2025: (Start)
E.g.f.: 6*exp(x)*(exp(5*x) - 1)/5.
a(n) = 6*(6^n - 1)/5.
a(n) = 6*A003464(n). (End)

Extensions

More terms from Harvey P. Dale, Jul 24 2012

A263133 Numbers m such that binomial(4*m + 3, m) is odd.

Original entry on oeis.org

0, 1, 2, 3, 5, 7, 10, 11, 15, 21, 23, 31, 42, 43, 47, 63, 85, 87, 95, 127, 170, 171, 175, 191, 255, 341, 343, 351, 383, 511, 682, 683, 687, 703, 767, 1023, 1365, 1367, 1375, 1407, 1535, 2047, 2730, 2731, 2735, 2751, 2815, 3071, 4095, 5461, 5463, 5471, 5503
Offset: 1

Views

Author

Peter Bala, Oct 11 2015

Keywords

Comments

The even terms in the sequence are A020988. If m is a term in the sequence then 2*m + 1 is also a term in the sequence. Repeatedly applying the transformation m -> 2*m + 1 to the terms of A020988 produces all the terms of this sequence. See the example below.
2*a(n) gives the values of m such that binomial(4*m + 6, m) is odd.

Examples

			1) This sequence can be read from Table 1 below in a sequence of 'knight moves' (2 down and 1 to the left) starting from the first two rows. For example, starting at 42 in the first row we jump 42 -> 43 -> 47 -> 63, then return to the second row at 85 and jump 85 -> 87 -> 95 -> 127, followed by 170 -> 171 -> 175 -> 191 -> 255, and so on.
...........................................................
. Table 1. 2^n*ceiling((2^(2*k + 1) - 1)/3) - 1, n,k >= 0 .
...........................................................
  n\k|   0    1    2    3    4    5
  ---+---------------------------------
   0 |   0    2   10   42  170  682 ...
   1 |   1    5   21   85  341  ...
   2 |   3   11   43  171  683  ...
   3 |   7   23   87  343  ...
   4 |  15   47  175  687  ...
   5 |  31   95  351  ...
   6 |  63  191  703  ...
   7 | 127  383  ...
   8 | 255  767  ...
   9 | 511  ...
   ...
The first row of the table is A020988. The columns of the table are obtained by repeatedly applying the transformation m -> 2*m + 1 to the entries in the first row.
2) Alternatively, this sequence can be read from Table 2 below by starting with a number on the top row and moving in a series of 'knight moves' (1 down and 2 to the left) through the table as far as you can, before returning to the next number in the top row and repeating the process. For example, starting at 10 in the first row we move 10 -> 11 -> 15, then return to the top row at 21 and move 21 -> 23 -> 31, before returning to the top row at 42 and so on.
........................................................
. Table 2. (4^n)*ceiling(2^k/3) - 1 for n >= 0, k >= 1 .
........................................................
n\k|    1    2    3    4     5     6     7     8    9   10
---+---------------------------------------------------------
  0|    0    1    2    5    10    21    42    85  170  682...
  1|    3    7   11   23    43    87   171   343  683  ...
  2|   15   31   47   95   175   351   687  1375  ...
  3|   63  127  191  383   703  1407  2751  5503  ...
  4|  255  511  767 1535  2815  5631 11007 22015  ...
  5| 1023 2047 3071 6143 11263 22527 44031 88063  ...
  6| 4095 ...
  ...
The first row of the table is A000975. The columns of the table are obtained by repeatedly applying the transformation m -> 4*m + 3 to the entries in the first row.
		

Crossrefs

Cf. A000975.
Other odd binomials: A263132 (4*m-1,m), A002450 (4*m+1,m), A020988 (4*m+2,m), A080674 (4*m+4,m), A118113 (3*m-2,m), A003714 (3*m,m).

Programs

  • Magma
    [n: n in [0..6000] | Binomial(4*n+3, n) mod 2 eq 1]; // Vincenzo Librandi, Oct 12 2015
    
  • Maple
    for n from 1 to 4096 do if mod(binomial(4*n+3, n), 2) = 1 then print(n) end if end do;
  • Mathematica
    Select[Range[0,5600],OddQ[Binomial[4#+3,#]]&] (* Harvey P. Dale, Apr 15 2019 *)
  • PARI
    for(n=0, 1e4, if (binomial(4*n+3, n) % 2 == 1, print1(n", "))) \\ Altug Alkan, Oct 11 2015
    
  • PARI
    a(n) = my(r,s=sqrtint(4*n-3,&r)); (1<Kevin Ryde, Jul 06 2025
    
  • Python
    A263133_list = [m for m in range(10**6) if not ~(4*m+3) & m] # Chai Wah Wu, Feb 07 2016

Formula

a(n) = A263132(n) - 1.
m is a term if and only if m AND NOT (4*m+3) = 0 where AND and NOT are bitwise operators. - Chai Wah Wu, Feb 07 2016
a(n) = (2^A000267(n) + 2^A384688(n))/3 - 1, for n >= 1. - Kevin Ryde, Jul 06 2025

Extensions

More terms from Vincenzo Librandi, Oct 12 2015

A105280 a(0)=0; a(n) = 11*a(n-1) + 11.

Original entry on oeis.org

0, 11, 132, 1463, 16104, 177155, 1948716, 21435887, 235794768, 2593742459, 28531167060, 313842837671, 3452271214392, 37974983358323, 417724816941564, 4594972986357215, 50544702849929376, 555991731349223147, 6115909044841454628, 67274999493256000919, 740024994425816010120
Offset: 0

Author

Alexandre Wajnberg, Apr 25 2005

Keywords

Crossrefs

Programs

  • Maple
    a:=n-> add(11^j,j=1..n): seq(a(n),n=0..12); # Zerinvary Lajos, Oct 03 2007
  • Mathematica
    NestList[11#+11&,0,20] (* or *) LinearRecurrence[{12,-11},{0,11},20] (* Harvey P. Dale, Dec 02 2023 *)

Formula

a(n) = 11^n + a(n-1) (with a(0)=0). - Vincenzo Librandi, Nov 13 2010
From Elmo R. Oliveira, May 24 2025: (Start)
G.f.: 11*x/((x-1)*(11*x-1)).
E.g.f.: 11*exp(x)*(exp(10*x) - 1)/10.
a(n) = 11*(11^n - 1)/10.
a(n) = 12*a(n-1) - 11*a(n-2).
a(n) = A016123(n) - 1. (End)

Extensions

Corrected by T. D. Noe, Nov 07 2006

A155721 Positions of parity change in A033035.

Original entry on oeis.org

4, 20, 84, 340, 1364, 5460, 21844, 87380, 349524, 1398100, 5592404, 22369620, 89478484, 357913940, 1431655764, 5726623060, 22906492244, 91625968980, 366503875924, 1466015503700, 5864062014804, 23456248059220, 93824992236884
Offset: 1

Author

Zak Seidov, Jan 25 2009

Keywords

Comments

Numbers n such that A033035(n)=(7/8)*(9^n - 1)=7*A002452(n).

Examples

			A033035(n=1..4) all are odd, then A033035(n=5..20) all are even, then A033035(n=21..84) all are odd, then A033035(n=85..340) all are even, etc.
		

Crossrefs

Formula

a(n=1,2..)=(4/3)*(4^n-1)=A080674(n).
a(n) = 5*a(n-1) - 4*a(n-2) for n > 2. G.f.: 4*x/((x - 1)*(4*x - 1)). - Chai Wah Wu, Aug 30 2019
Previous Showing 11-16 of 16 results.