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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A017293 a(n) = 10*n + 2.

Original entry on oeis.org

2, 12, 22, 32, 42, 52, 62, 72, 82, 92, 102, 112, 122, 132, 142, 152, 162, 172, 182, 192, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 302, 312, 322, 332, 342, 352, 362, 372, 382, 392, 402, 412, 422, 432, 442, 452, 462, 472, 482, 492, 502, 512, 522, 532
Offset: 0

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Author

N. J. A. Sloane, Dec 11 1996

Keywords

Comments

Number of 5 X n 0-1 matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (00;1), (01;0), (11;0) and (01;1). An occurrence of a ranpp (xy;z) in a matrix A=(a(i,j)) is a triple (a(i1,j1), a(i1,j2), a(i2,j1)) where i1A008574; m=3: A016933; m=4: A022144; m=6: A017569. - Sergey Kitaev, Nov 13 2004

Crossrefs

Programs

Formula

a(n) = 2*A016861(n) = A008592(n) + 2. - Wesley Ivan Hurt, May 03 2014
G.f.: 2*(1 + 4*x)/(1-x)^2. - Vincenzo Librandi, Jul 23 2016
From Elmo R. Oliveira, Apr 04 2025: (Start)
E.g.f.: 2*exp(x)*(1 + 5*x).
a(n) = 2*a(n-1) - a(n-2) for n >= 2.
a(n) = A016873(2*n). (End)

A089911 a(n) = Fibonacci(n) mod 12.

Original entry on oeis.org

0, 1, 1, 2, 3, 5, 8, 1, 9, 10, 7, 5, 0, 5, 5, 10, 3, 1, 4, 5, 9, 2, 11, 1, 0, 1, 1, 2, 3, 5, 8, 1, 9, 10, 7, 5, 0, 5, 5, 10, 3, 1, 4, 5, 9, 2, 11, 1, 0, 1, 1, 2, 3, 5, 8, 1, 9, 10, 7, 5, 0, 5, 5, 10, 3, 1, 4, 5, 9, 2, 11, 1, 0, 1, 1, 2, 3, 5, 8, 1, 9, 10, 7, 5, 0, 5, 5, 10, 3, 1, 4, 5, 9, 2, 11, 1, 0, 1, 1
Offset: 0

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Author

Casey Mongoven, Nov 14 2003

Keywords

Comments

From Reinhard Zumkeller, Jul 05 2013: (Start)
Sequence has been applied by several composers to 12-tone equal temperament pitch structure. The complete Fibonacci mod 12 system (a set of 10 periodic sequences) exhausts all possible ordered dyads; that is, every possible combination of two pitches is found in these sets.
a(A008594(n)) = 0;
a(A227144(n)) = 1;
a(3*A047522(n)) = 2;
a(A017569(n)) = a(2*A016933(n)) = a(4*A016777(n)) = 3;
a(2*A017629(n)) = a(3*A017137(n)) = a(6*A004767(n)) = 4;
a(A227146(n)) = 5;
a(nonexistent) = 6;
a(2*A017581(n)) = 7;
a(2*A017557(n)) = a(4*A016813(n)) = 8;
a(A017617(n)) = a(2*A016957(n)) = a(4*A016789(n)) = 9;
a(3*A047621(n)) = 10;
a(2*A017653(n)) = 11. (End)

Crossrefs

Programs

  • Haskell
    a089911 n = a089911_list !! n
    a089911_list = 0 : 1 : zipWith (\u v -> (u + v) `mod` 12)
                           (tail a089911_list) a089911_list
    -- Reinhard Zumkeller, Jul 01 2013
    
  • Magma
    [Fibonacci(n) mod 12: n in [0..100]]; // Vincenzo Librandi, Feb 04 2014
  • Maple
    with(combinat,fibonacci); A089911 := proc(n) fibonacci(n) mod 12; end;
  • Mathematica
    Table[Mod[Fibonacci[n], 12], {n, 0, 100}] (* Vincenzo Librandi, Feb 04 2014 *)
  • PARI
    a(n)=fibonacci(n)%12 \\ Charles R Greathouse IV, Feb 03 2014
    

Formula

Has period of 24, restricted period 12 and multiplier 5.
a(n) = (a(n-1) + a(n-2)) mod 12, a(0) = 0, a(1) = 1.

Extensions

More terms from Ray Chandler, Nov 15 2003

A013730 a(n) = 2^(3*n+1).

Original entry on oeis.org

2, 16, 128, 1024, 8192, 65536, 524288, 4194304, 33554432, 268435456, 2147483648, 17179869184, 137438953472, 1099511627776, 8796093022208, 70368744177664, 562949953421312, 4503599627370496, 36028797018963968, 288230376151711744, 2305843009213693952, 18446744073709551616
Offset: 0

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Author

Keywords

Comments

1/2 + 1/16 + 1/128 + 1/1024 + ... = 4/7. - Gary W. Adamson, Aug 29 2008

Crossrefs

Programs

Formula

From Philippe Deléham, Nov 23 2008: (Start)
a(n) = 8*a(n-1), n > 0; a(0)=2.
G.f.: 2/(1-8x). (End)
a(n) = A157176(A016921(n)) = A157176(A016933(n)). - Reinhard Zumkeller, Feb 24 2009
From Amiram Eldar, May 08 2023: (Start)
Sum_{n>=0} (-1)^n/a(n) = 4/9.
Product_{n>=0} (1 - 1/a(n)) = A132024. (End)
E.g.f.: 2*exp(8*x). - Stefano Spezia, May 29 2024

A017569 a(n) = 12*n + 4.

Original entry on oeis.org

4, 16, 28, 40, 52, 64, 76, 88, 100, 112, 124, 136, 148, 160, 172, 184, 196, 208, 220, 232, 244, 256, 268, 280, 292, 304, 316, 328, 340, 352, 364, 376, 388, 400, 412, 424, 436, 448, 460, 472, 484, 496, 508, 520, 532, 544, 556, 568, 580, 592, 604, 616, 628
Offset: 0

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Author

Keywords

Comments

Apart from initial term(s), dimension of the space of weight 2n cusp forms for Gamma_0(46).
Number of 6 X n 0-1 matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (00;1), (01;0), (11;0) and (01;1). An occurrence of a ranpp (xy;z) in a matrix A=(a(i,j)) is a triple (a(i1,j1), a(i1,j2), a(i2,j1)) where i1A008574; m=3: A016933; m=4: A022144; m=5: A017293. - Sergey Kitaev, Nov 13 2004
Except for 4, exponents e such that x^e - x^2 + 1 is reducible.
If Y and Z are 2-blocks of a (3n+1)-set X then a(n-1) is the number of 3-subsets of X intersecting both Y and Z. - Milan Janjic, Oct 28 2007
Terms are perfect squares iff n is a generalized octagonal number (A001082), then n = k*(3*k-2) and a(n) = (2*(3*k-1))^2. - Bernard Schott, Feb 26 2023

Crossrefs

Programs

Formula

A089911(a(n)) = 3. - Reinhard Zumkeller, Jul 05 2013
Sum_{n>=0} (-1)^n/a(n) = sqrt(3)*Pi/36 + log(2)/12. - Amiram Eldar, Dec 12 2021
From Stefano Spezia, Feb 25 2023: (Start)
O.g.f.: 4*(1 + 2*x)/(1 - x)^2.
E.g.f.: 4*exp(x)*(1 + 3*x). (End)
From Elmo R. Oliveira, Apr 10 2025: (Start)
a(n) = 2*a(n-1) - a(n-2).
a(n) = 2*A016933(n) = 4*A016777(n) = A016777(4*n+1). (End)

A016935 a(n) = (6*n + 2)^3.

Original entry on oeis.org

8, 512, 2744, 8000, 17576, 32768, 54872, 85184, 125000, 175616, 238328, 314432, 405224, 512000, 636056, 778688, 941192, 1124864, 1331000, 1560896, 1815848, 2097152, 2406104, 2744000, 3112136
Offset: 0

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Author

Keywords

Comments

The generating function is 8 times the g.f. of A016779. - R. J. Mathar, May 07 2008

Examples

			a(1) = (6*1 + 2)^3 = 8^3 = 512.
		

Crossrefs

Programs

  • Magma
    [(6*n+2)^3: n in [0..50]]; // Vincenzo Librandi, May 04 2011
  • Mathematica
    (6*Range[0,30]+2)^3 (* or *) LinearRecurrence[{4,-6,4,-1},{8,512,2744,8000},30] (* Harvey P. Dale, Aug 23 2019 *)

Formula

a(n) = 8*A016779(n). - R. J. Mathar, May 07 2008
Sum_{n>=0} 1/a(n) = Pi^3 / (324*sqrt(3)) + 13*zeta(3)/216. - Amiram Eldar, Oct 02 2020
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4). - Wesley Ivan Hurt, Oct 02 2020
G.f.: 8*(1+60*x+93*x^2+8*x^3)/(-1+x)^4. - Wesley Ivan Hurt, Oct 02 2020

A017617 a(n) = 12*n + 8.

Original entry on oeis.org

8, 20, 32, 44, 56, 68, 80, 92, 104, 116, 128, 140, 152, 164, 176, 188, 200, 212, 224, 236, 248, 260, 272, 284, 296, 308, 320, 332, 344, 356, 368, 380, 392, 404, 416, 428, 440, 452, 464, 476, 488, 500, 512, 524, 536, 548, 560, 572, 584, 596, 608, 620, 632, 644, 656
Offset: 0

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Author

Keywords

Comments

Also the number of cube units that frame a cube of edge length n+1. - Peter M. Chema, Mar 27 2016

Examples

			For n=3; a(3)= 12*3 + 8 = 44.
Thus, there are 44 cube units that frame a cube of edge length 4. - _Peter M. Chema_, Mar 26 2016
		

Crossrefs

Programs

Formula

a(n) = 2*a(n-1) - a(n-2). - Vincenzo Librandi, Jun 08 2011
A089911(a(n)) = 9. - Reinhard Zumkeller, Jul 05 2013
G.f.: 12*x/(1-x)^2 + 8/(1-x) = 4*(2+x)/(1-x)^2. (see the PARI program). - Wolfdieter Lang, Oct 11 2021
Sum_{n>=0} (-1)^n/a(n) = sqrt(3)*Pi/36 - log(2)/12. - Amiram Eldar, Dec 12 2021
From Elmo R. Oliveira, Apr 04 2025: (Start)
E.g.f.: 4*exp(x)*(2 + 3*x).
a(n) = 4*A016789(n) = 2*A016957(n) = A016933(2*n+1). (End)

A339013 Class number m containing n in a partitioning of the natural numbers into classes B_m by William J. Keith.

Original entry on oeis.org

2, 3, 2, 4, 2, 4, 2, 3, 2, 5, 2, 5, 2, 3, 2, 5, 2, 5, 2, 3, 2, 5, 2, 5, 2, 3, 2, 4, 2, 4, 2, 3, 2, 6, 2, 6, 2, 3, 2, 6, 2, 6, 2, 3, 2, 6, 2, 6, 2, 3, 2, 4, 2, 4, 2, 3, 2, 6, 2, 6, 2, 3, 2, 6, 2, 6, 2, 3, 2, 6, 2, 6, 2, 3, 2, 4, 2, 4, 2, 3, 2, 6, 2, 6, 2, 3, 2
Offset: 1

Views

Author

Kevin Ryde, Nov 19 2020

Keywords

Comments

a(n)=m when n is in class B_m. Keith's residues formula in lemma 1 is equivalent to requiring that n-1 in factorial base representation ends in m-2 nonzero digits, so m = A339012(n-1) + 2.
a(n)=m iff n mod m! is among certain residue classes determined by m. The residues for A339012 are rows of A227157 and here add +1 to each residue (mod m!). For example 3 or 5 (mod 24) in A339012 becomes here 4 or 6 (mod 24).
The frequency of appearance of the term k = 2, 3, ... in this sequence is 1/(k*(k-1)). - Amiram Eldar, Feb 15 2021

Crossrefs

Cf. A005408 (class B_2), A016933 (class B_3).
Cf. A161189 (class number in partition A_k), A339012.

Programs

  • Mathematica
    a[n_] := Module[{k = n - 1, m = 2, r}, While[{k, r} = QuotientRemainder[k, m]; r != 0, m++]; m]; Array[a, 30] (* Amiram Eldar, Feb 15 2021 after Kevin Ryde's PARI code *)
  • PARI
    a(n) = n--; my(b=2,r); while([n,r]=divrem(n,b);r!=0, b++); b;

Formula

a(n) = A339012(n-1) + 2.
a(n) = m iff n == 1 + Sum_{j=1..m-2} d[j]*j! (mod m!) with d[j] in ranges 1 <= d[j] <= j. [Keith, section 2.1 lemma 1]
a(n)=2 iff n mod 2 = 1. [Keith section 4 residues].
a(n)=3 iff n mod 6 = 2.
a(n)=4 iff n mod 24 = 4 or 6.
a(n)=5 iff n mod 120 = any of 10, 12, 16, 18, 22, 24.

A144390 a(n) = 3*n^2 - n - 1.

Original entry on oeis.org

1, 9, 23, 43, 69, 101, 139, 183, 233, 289, 351, 419, 493, 573, 659, 751, 849, 953, 1063, 1179, 1301, 1429, 1563, 1703, 1849, 2001, 2159, 2323, 2493, 2669, 2851, 3039, 3233, 3433, 3639, 3851, 4069, 4293, 4523, 4759, 5001, 5249, 5503, 5763, 6029, 6301, 6579
Offset: 1

Views

Author

Paul Curtz, Oct 02 2008

Keywords

Comments

Sequence's original Name was "First bisection of A135370."
The partial sums of this sequence give A081437. - Leo Tavares, Dec 26 2021

Crossrefs

Cf. A081437 (partial sums).

Programs

Formula

a(n+1) = a(n) + 6*n + 2; see A016933.
G.f.: x*(1+6*x-x^2)/(1-x)^3. a(n) = A049450(n)-1. - R. J. Mathar, Oct 24 2008
a(-n) = A144391(n). - Michael Somos, Mar 27 2014
E.g.f.: (3*x^2 + 2*x -1)*exp(x) + 1. - G. C. Greubel, Jul 19 2017
From Leo Tavares, Dec 26 2021: (Start)
a(n) = A003215(n) - 2*A005408(n). See Bounded Hexagons illustration.
a(n) = A016754(n-1) - A002378(n-2). (End)
a(n) = A003154(n) - A049451(n-1). - John Elias, Dec 22 2022

Extensions

Edited by R. J. Mathar, Oct 24 2008
More terms from Vladimir Joseph Stephan Orlovsky, Oct 25 2008

A016934 a(n) = (6*n + 2)^2.

Original entry on oeis.org

4, 64, 196, 400, 676, 1024, 1444, 1936, 2500, 3136, 3844, 4624, 5476, 6400, 7396, 8464, 9604, 10816, 12100, 13456, 14884, 16384, 17956, 19600, 21316, 23104, 24964, 26896, 28900, 30976, 33124, 35344, 37636, 40000, 42436, 44944, 47524, 50176, 52900, 55696, 58564
Offset: 0

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Author

Keywords

Crossrefs

Programs

Formula

Sum_{n>=0} 1/a(n) = A086728. - Amiram Eldar, Nov 16 2020
From Stefano Spezia, Feb 21 2025: (Start)
G.f.: 4*(1 + 13*x + 4*x^2)/(1 - x)^3.
E.g.f.: 4*exp(x)*(1 + 15*x + 9*x^2). (End)

A221683 T(n,k)=Number of 0..k arrays of length n with each element differing from at least one neighbor by 1 or less, starting with 0.

Original entry on oeis.org

0, 0, 2, 0, 2, 4, 0, 2, 5, 8, 0, 2, 5, 14, 16, 0, 2, 5, 20, 40, 32, 0, 2, 5, 26, 68, 113, 64, 0, 2, 5, 32, 100, 241, 320, 128, 0, 2, 5, 38, 133, 418, 844, 906, 256, 0, 2, 5, 44, 166, 636, 1692, 2966, 2565, 512, 0, 2, 5, 50, 199, 891, 2856, 6932, 10413, 7262, 1024, 0, 2, 5, 56, 232
Offset: 1

Views

Author

R. H. Hardin Jan 22 2013

Keywords

Comments

Table starts
....0.....0......0.......0.......0........0........0........0........0
....2.....2......2.......2.......2........2........2........2........2
....4.....5......5.......5.......5........5........5........5........5
....8....14.....20......26......32.......38.......44.......50.......56
...16....40.....68.....100.....133......166......199......232......265
...32...113....241.....418.....636......891.....1182.....1509.....1872
...64...320....844....1692....2856.....4326.....6102.....8184....10572
..128...906...2966....6932...13169....21985....33710....48674....67202
..256..2565..10413...28288...60120...109567...180382...276317...401105
..512..7262..36568..115604..275632...551027...980490..1606710..2476200
.1024.20560.128408..472188.1261451..2759757..5289023..9228224.15012528
.2048.58209.450913.1929012.5777107.13846871.28634131.53334307.91896348

Examples

			Some solutions for n=6 k=4
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....0....1....1....1....1....0....0....0....0....1....0....0....0....0....1
..2....0....0....0....4....1....4....4....0....2....1....1....1....0....0....2
..1....2....3....1....3....2....3....3....1....3....3....1....2....0....1....3
..1....1....4....2....2....1....2....3....4....2....3....1....1....0....1....0
..0....2....4....2....1....0....3....4....4....2....4....2....1....1....2....1
		

Crossrefs

Row 4 is A016933

Formula

Empirical for column k:
k=1: a(n) = 2*a(n-1) for n>2
k=2: a(n) = 2*a(n-1) +2*a(n-2) +a(n-3)
k=3: a(n) = 3*a(n-1) +2*a(n-2) -a(n-3) +a(n-4)
k=4: a(n) = 3*a(n-1) +4*a(n-2) +6*a(n-4) +4*a(n-5) +4*a(n-6)
k=5: a(n) = 4*a(n-1) +3*a(n-2) -6*a(n-3) +19*a(n-4) +5*a(n-5) +a(n-6)
k=6: a(n) = 4*a(n-1) +5*a(n-2) -7*a(n-3) +33*a(n-4) +17*a(n-5) +24*a(n-6) -5*a(n-7) +2*a(n-8)
k=7: a(n) = 5*a(n-1) +3*a(n-2) -16*a(n-3) +65*a(n-4) -14*a(n-5) +23*a(n-6) +2*a(n-7) +8*a(n-8)
Empirical for row n:
n=1: a(n) = 0
n=2: a(n) = 2
n=3: a(n) = 5 for n>1
n=4: a(n) = 6*n + 2
n=5: a(n) = 33*n - 32 for n>3
n=6: a(n) = 18*n^2 + 57*n - 99 for n>4
n=7: a(n) = 153*n^2 - 213*n + 96 for n>3
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