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 1-10 of 13 results. Next

A246517 Indices of primes in A141036.

Original entry on oeis.org

0, 5, 14, 26, 33, 222, 234, 482, 937, 1170, 1290, 1877, 1897, 3413, 6017, 9365, 47470, 48254, 97421, 102057, 119689, 132418, 192517, 194442
Offset: 1

Views

Author

Robert Price, Aug 28 2014

Keywords

Comments

a(25) > 2*10^5.
A141036(a(n)) = A246518(n).

Crossrefs

Programs

  • Haskell
    a246517 n = a246517_list !! (n-1)
    a246517_list = filter ((== 1) . a010051'' . a141036) [0..]
    -- Reinhard Zumkeller, Sep 15 2014
  • Mathematica
    a={2,1,1}; Print[0]; For[n=3, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[n]]; a=RotateLeft[a]; a[[3]]=sum]

A246518 Prime terms in A141036.

Original entry on oeis.org

2, 11, 2713, 4066709, 289593761, 30236674150891013353640837416685668536004108580572237299601, 45323907186142905348893078704293178796516046414129798590935901
Offset: 1

Views

Author

Robert Price, Aug 28 2014

Keywords

Comments

a(8) has 91 digits and thus is too large to display here. It corresponds to A141036(482).
a(n) = A141036(A246517(n)).

Crossrefs

Programs

  • Haskell
    a246518 n = a246518_list !! (n-1)
    a246518_list = filter ((== 1) . a010051'') $ a141036_list
    -- Reinhard Zumkeller, Sep 15 2014
  • Mathematica
    a={2,1,1}; Print[2]; For[n=3, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[sum]]; a=RotateLeft[a]; a[[3]]=sum]

A144458 Two sequence determinant triangle sequence: a(n)=A000045(n); b(n)=b(n-1)+b(n-2)+b(n-3) :2 start;A141036(n); t(n,m)=t(n,m)=a(m)*b(n)-b(m)*a(n).

Original entry on oeis.org

-2, -2, 0, -4, 2, 2, -6, 3, 3, 0, -10, 6, 6, 2, 3, -16, 13, 13, 10, 15, 17, -26, 25, 25, 24, 36, 47, 31, -42, 49, 49, 56, 84, 119, 119, 112, -68, 95, 95, 122, 183, 271, 318, 385, 329, -110, 182, 182, 254, 381, 580, 741, 991, 1127, 963
Offset: 1

Views

Author

Roger L. Bagula and Gary W. Adamson, Oct 07 2008

Keywords

Comments

Row sums are:{-2, -2, 0, 0, 7, 52, 162, 546, 1730, 5291}.
Reasoning behind the sequence is:
Suppose we have n affine transforms that form a group:
g={ a(1)*x+b(1),a(2)*x+b(2),...,a(n)*x+b(n)}
on the sequences a(n) and b(n).
We form rational projections as Moebius / bilinear transforms:
g(projection)={( a(1)*x+b(1))/(a(n)*x+b(n)),( a(2)*x+b(2))/(a(n)*x+b(n)),...,( a(n-1)*x+b(n-1))/(a(n)*x+b(n))
With determinants:
g_det={a(1)*b(n)-b(1)*a(n),a(2)*b(n)-b(2)*a(n),...,a(n-1)*b(n)-b(n-1)*a(n)}
So that we have the triangular sequences:
t(n,m)=a(m)*b(n)-b(m)*a(n)

Examples

			{-2},
{-2, 0},
{-4, 2, 2},
{-6, 3, 3, 0},
{-10, 6, 6, 2, 3},
{-16, 13, 13, 10, 15, 17},
{-26, 25, 25, 24, 36, 47, 31},
{-42, 49, 49, 56, 84, 119, 119, 112},
{-68, 95, 95, 122, 183, 271, 318, 385, 329},
{-110, 182, 182, 254, 381, 580, 741, 991, 1127, 963}
		

Crossrefs

Programs

  • Mathematica
    Clear[a, b, t, n, m] a[n_] := Fibonacci[n]; b[0] = 2; b[1] = 1; b[2] = 1; b[n_] := b[n] = b[n - 1] + b[n - 2] + b[n - 3]; t[n_, m_] := a[m]*b[n] - b[m]*a[n]; Table[Table[t[n, m], {m, 0, n - 1}], {n, 1, 10}]; Flatten[%]

Formula

a(n)=A000045(n); b(n)=b(n-1)+b(n-2)+b(n-3) :2 start;A141036; t(n,m)=t(n,m)=a(m)*b(n)-b(m)*a(n).

A214727 a(n) = a(n-1) + a(n-2) + a(n-3) with a(0) = 1, a(1) = a(2) = 2.

Original entry on oeis.org

1, 2, 2, 5, 9, 16, 30, 55, 101, 186, 342, 629, 1157, 2128, 3914, 7199, 13241, 24354, 44794, 82389, 151537, 278720, 512646, 942903, 1734269, 3189818, 5866990, 10791077, 19847885, 36505952, 67144914, 123498751, 227149617, 417793282
Offset: 0

Views

Author

Abel Amene, Jul 27 2012

Keywords

Comments

Part of a group of sequences defined by a(0), a(1)=a(2), a(n) = a(n-1) + a(n-2) + a(n-3) which is a subgroup of sequences with linear recurrences and constant coefficients listed in the index.
Note: A000073 (with offset=1), 1 followed by A000073, A000213, A141523, A214727, A214825 to A214831 completely define possible sequences with a(0)=0,1,2...9 and a(1)=a(2)=0,1,2...9 excluding any multiples of these sequences and the trivial case of a(0)=a(1)=a(2)=0.
Note: allowing a(0)=0 and a(1)=a(2)=1,2,3....9 leads to A000073 (with offset=1) and its multiples.
Note: allowing a(0)=1,2,3....9 a(1)=a(2)=0 leads to 1 followed by A000073 and its multiples.
With offset of 6 this sequence is the 8th row of tribonacci array A136175.

Examples

			G.f. = 1 + 2*x + 2*x^2 + 5 x^3 + 9*x^4 + 16*x^5 + 30*x^6 + 55*x^7 + ...
		

Crossrefs

Programs

  • GAP
    a:=[1,2,2];; for n in [4..40] do a[n]:=a[n-1]+a[n-2]+a[n-3]; od; a; # G. C. Greubel, Apr 23 2019
  • Haskell
    a214727 n = a214727_list !! n
    a214727_list = 1 : 2 : 2 : zipWith3 (\x y z -> x + y + z)
       a214727_list (tail a214727_list) (drop 2 a214727_list)
    -- Reinhard Zumkeller, Jul 31 2012
    
  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+x-x^2)/(1-x-x^2-x^3) )); // G. C. Greubel, Apr 23 2019
    
  • Mathematica
    LinearRecurrence[{1,1,1},{1,2,2},40] (* Ray Chandler, Dec 08 2013 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 1,1,1]^n*[1;2;2])[1,1] \\ Charles R Greathouse IV, Mar 22 2016
    
  • PARI
    my(x='x+O('x^40)); Vec((1+x-x^2)/(1-x-x^2-x^3)) \\ G. C. Greubel, Apr 23 2019
    
  • SageMath
    ((1+x-x^2)/(1-x-x^2-x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 23 2019
    

Formula

G.f.: (1+x-x^2)/(1-x-x^2-x^3).
a(n) = K(n) -2*T(n+1) + 3*T(n), where K(n) = A001644(n), T(n) = A000073(n+1). - G. C. Greubel, Apr 23 2019
a(n) = Sum_{r root of x^3-x^2-x-1} r^n/(-r^2+2*r+1). - Fabian Pereyra, Nov 20 2024

A214899 a(n) = a(n-1) + a(n-2) + a(n-3) with a(0)=2, a(1)=1, a(2)=2.

Original entry on oeis.org

2, 1, 2, 5, 8, 15, 28, 51, 94, 173, 318, 585, 1076, 1979, 3640, 6695, 12314, 22649, 41658, 76621, 140928, 259207, 476756, 876891, 1612854, 2966501, 5456246, 10035601, 18458348, 33950195, 62444144, 114852687, 211247026, 388543857
Offset: 0

Views

Author

Abel Amene, Jul 29 2012

Keywords

Comments

With offset of 5 this sequence is the 4th row of the tribonacci array A136175.
For n>0, a(n) is the number of ways to tile a strip of length n with squares, dominoes, and trominoes, such that there must be exactly one "special" square (say, of a different color) in the first three cells. - Greg Dresden and Emma Li, Aug 17 2024
From Greg Dresden and Jiarui Zhou, Jun 30 2025: (Start)
For n >= 3, a(n) is the number of ways to tile this shape of length n-1 with squares, dominos, and trominos (of length 3):
._
|||_|||_|||
|_|
As an example, here is one of the a(9) = 173 ways to tile this shape of length 8:
._
|| |__|_|___|
|_|. (End)

Crossrefs

Programs

  • GAP
    a:=[2,1,2];; for n in [4..40] do a[n]:=a[n-1]+a[n-2]+a[n-3]; od; a; # G. C. Greubel, Apr 23 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (2-x-x^2)/(1-x-x^2-x^3) )); // G. C. Greubel, Apr 23 2019
    
  • Mathematica
    LinearRecurrence[{1,1,1},{2,1,2},34] (* Ray Chandler, Dec 08 2013 *)
  • PARI
    a(n)=([0,1,0;0,0,1;1,1,1]^n*[2;1;2])[1,1] \\ Charles R Greathouse IV, Jun 11 2015
    
  • PARI
    my(x='x+O('x^40)); Vec((2-x-x^2)/(1-x-x^2-x^3)) \\ G. C. Greubel, Apr 23 2019
    
  • Sage
    ((2-x-x^2)/(1-x-x^2-x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 23 2019
    

Formula

G.f.: (2-x-x^2)/(1-x-x^2-x^3).
a(n) = K(n) - T(n+1) + T(n), where K(n) = A001644(n), T(n) = A000073(n+1). - G. C. Greubel, Apr 23 2019

A214825 a(n) = a(n-1) + a(n-2) + a(n-3), with a(0) = 1, a(1) = a(2) = 3.

Original entry on oeis.org

1, 3, 3, 7, 13, 23, 43, 79, 145, 267, 491, 903, 1661, 3055, 5619, 10335, 19009, 34963, 64307, 118279, 217549, 400135, 735963, 1353647, 2489745, 4579355, 8422747, 15491847, 28493949, 52408543, 96394339, 177296831, 326099713, 599790883, 1103187427
Offset: 0

Views

Author

Abel Amene, Jul 28 2012

Keywords

Comments

Part of a group of sequences defined by a(0), a(1)=a(2), a(n) = a(n-1) + a(n-2) + a(n-3) which is a subgroup of sequences with linear recurrences and constant coefficients listed in the index. See Comments in A214727.

Crossrefs

Programs

  • GAP
    a:=[1,3,3];; for n in [4..40] do a[n]:=a[n-1]+a[n-2]+a[n-3]; od; a; # G. C. Greubel, Apr 23 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+2*x-x^2)/(1-x-x^2-x^3) )); // G. C. Greubel, Apr 23 2019
    
  • Mathematica
    LinearRecurrence[{1,1,1},{1,3,3},40] (* Harvey P. Dale, Oct 05 2013 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 1,1,1]^n*[1;3;3])[1,1] \\ Charles R Greathouse IV, Mar 22 2016
    
  • PARI
    my(x='x+O('x^40)); Vec((1+2*x-x^2)/(1-x-x^2-x^3)) \\ G. C. Greubel, Apr 23 2019
    
  • SageMath
    ((1+2*x-x^2)/(1-x-x^2-x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 23 2019
    

Formula

G.f.: (1+2*x-x^2)/(1-x-x^2-x^3).
a(n) = K(n) - 2*T(n+1) + 4*T(n), where K(n) = A001644(n), and T(n) = A000073(n+1). - G. C. Greubel, Apr 23 2019

A214827 a(n) = a(n-1) + a(n-2) + a(n-3), with a(0) = 1, a(1) = a(2) = 5.

Original entry on oeis.org

1, 5, 5, 11, 21, 37, 69, 127, 233, 429, 789, 1451, 2669, 4909, 9029, 16607, 30545, 56181, 103333, 190059, 349573, 642965, 1182597, 2175135, 4000697, 7358429, 13534261, 24893387, 45786077, 84213725, 154893189, 284892991, 523999905
Offset: 0

Views

Author

Abel Amene, Jul 29 2012

Keywords

Comments

See comments in A214727.

Crossrefs

Programs

  • GAP
    a:=[1,5,5];; for n in [4..40] do a[n]:=a[n-1]+a[n-2]+a[n-3]; od; a; # G. C. Greubel, Apr 24 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+4*x-x^2)/(1-x-x^2-x^3) )); // G. C. Greubel, Apr 24 2019
    
  • Mathematica
    LinearRecurrence[{1,1,1},{1,5,5},40] (* Ray Chandler, Dec 08 2013 *)
  • PARI
    my(x='x+O('x^40)); Vec((1+4*x-x^2)/(1-x-x^2-x^3)) \\ G. C. Greubel, Apr 24 2019
    
  • Sage
    ((1+4*x-x^2)/(1-x-x^2-x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 24 2019
    

Formula

G.f.: (x^2-4*x-1)/(x^3+x^2+x-1).
a(n) = -A000073(n) + 4*A000073(n+1) + A000073(n+2). - R. J. Mathar, Jul 29 2012

A214831 a(n) = a(n-1) + a(n-2) + a(n-3), with a(0) = 1, a(1) = a(2) = 9.

Original entry on oeis.org

1, 9, 9, 19, 37, 65, 121, 223, 409, 753, 1385, 2547, 4685, 8617, 15849, 29151, 53617, 98617, 181385, 333619, 613621, 1128625, 2075865, 3818111, 7022601, 12916577, 23757289, 43696467, 80370333, 147824089, 271890889, 500085311, 919800289, 1691776489
Offset: 0

Views

Author

Abel Amene, Aug 07 2012

Keywords

Comments

Part of a group of sequences defined by a(0), a(1)=a(2), a(n)=a(n-1)+a(n-2)+a(n-3) which is a subgroup of sequences with linear recurrences and constant coefficients listed in the index. See comments in A214727.

Crossrefs

Programs

  • GAP
    a:=[1,9,9];; for n in [4..40] do a[n]:=a[n-1]+a[n-2]+a[n-3]; od; a; # G. C. Greubel, Apr 24 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+8*x-x^2)/(1-x-x^2-x^3) )); // G. C. Greubel, Apr 24 2019
    
  • Mathematica
    LinearRecurrence[{1,1,1},{1,9,9},40] (* Harvey P. Dale, Oct 11 2017 *)
  • PARI
    Vec((x^2-8*x-1)/(x^3+x^2+x-1) + O(x^40)) \\ Michel Marcus, Jul 08 2014
    
  • SageMath
    ((1+8*x-x^2)/(1-x-x^2-x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 24 2019
    

Formula

G.f.: (1+8*x-x^2)/(1-x-x^2-x^3).
a(n) = -A000073(n) + 8*A000073(n+1) + A000073(n+2). - G. C. Greubel, Apr 24 2019

A214828 a(n) = a(n-1) + a(n-2) + a(n-3), with a(0) = 1, a(1) = a(2) = 6.

Original entry on oeis.org

1, 6, 6, 13, 25, 44, 82, 151, 277, 510, 938, 1725, 3173, 5836, 10734, 19743, 36313, 66790, 122846, 225949, 415585, 764380, 1405914, 2585879, 4756173, 8747966, 16090018, 29594157, 54432141, 100116316, 184142614, 338691071, 622950001
Offset: 0

Views

Author

Abel Amene, Jul 30 2012

Keywords

Comments

See comments in A214727.

Crossrefs

Programs

  • GAP
    a:=[1,6,6];; for n in [4..40] do a[n]:=a[n-1]+a[n-2]+a[n-3]; od; a; # G. C. Greubel, Apr 24 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+5*x-x^2)/(1-x-x^2-x^3) )); // G. C. Greubel, Apr 24 2019
    
  • Mathematica
    LinearRecurrence[{1,1,1},{1,6,6},33] (* Ray Chandler, Dec 08 2013 *)
  • PARI
    my(x='x+O('x^40)); Vec((1+5*x-x^2)/(1-x-x^2-x^3)) \\ G. C. Greubel, Apr 24 2019
    
  • Sage
    ((1+5*x-x^2)/(1-x-x^2-x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 24 2019
    

Formula

G.f.: (1+5*x-x^2)/(1-x-x^2-x^3).
a(n) = -A000073(n) + 5*A000073(n+1) + A000073(n+2). - G. C. Greubel, Apr 24 2019

A214829 a(n) = a(n-1) + a(n-2) + a(n-3), with a(0) = 1, a(1) = a(2) = 7.

Original entry on oeis.org

1, 7, 7, 15, 29, 51, 95, 175, 321, 591, 1087, 1999, 3677, 6763, 12439, 22879, 42081, 77399, 142359, 261839, 481597, 885795, 1629231, 2996623, 5511649, 10137503, 18645775, 34294927, 63078205, 116018907, 213392039, 392489151, 721900097, 1327781287, 2442170535
Offset: 0

Views

Author

Abel Amene, Aug 07 2012

Keywords

Comments

See comments in A214727.

Crossrefs

Programs

  • GAP
    a:=[1,7,7];; for n in [4..40] do a[n]:=a[n-1]+a[n-2]+a[n-3]; od; a; # G. C. Greubel, Apr 24 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+6*x-x^2)/(1-x-x^2-x^3) )); // G. C. Greubel, Apr 24 2019
    
  • Mathematica
    LinearRecurrence[{1,1,1}, {1,7,7}, 40] (* G. C. Greubel, Apr 24 2019 *)
  • PARI
    Vec((x^2-6*x-1)/(x^3+x^2+x-1) + O(x^40)) \\ Michel Marcus, Jun 04 2017
    
  • Sage
    ((1+6*x-x^2)/(1-x-x^2-x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 24 2019
    

Formula

G.f.: (1+6*x-x^2)/(1-x-x^2-x^3).
a(n) = -A000073(n) + 6*A000073(n+1) + A000073(n+2). - G. C. Greubel, Apr 24 2019
Showing 1-10 of 13 results. Next