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 48 results. Next

A230016 Indices of primes in the tribonacci-like sequence, A214825.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 10, 16, 17, 26, 32, 104, 109, 120, 133, 312, 546, 608, 2274, 2527, 2932, 4462, 4680, 6001, 7103, 17402, 17874, 20664, 26341, 27954, 32869, 36204, 41521, 49065, 64172, 66318, 196078
Offset: 1

Views

Author

Robert Price, Feb 22 2014

Keywords

Comments

a(39) > 2*10^5.

Crossrefs

Programs

  • Mathematica
    a={1,3,3}; Print[1];Print[2]; For[n=3, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[n]]; a=RotateLeft[a]; a[[3]]=sum]

A230017 Prime terms in the tribonacci-like sequence, A214825.

Original entry on oeis.org

3, 3, 7, 13, 23, 43, 79, 491, 19009, 34963, 8422747, 326099713, 3699221592878859104602113553, 77867739062209443974741001359, 63460200981504216633346603450897, 174962190954783387911511685367053207
Offset: 1

Views

Author

Robert Price, Feb 22 2014

Keywords

Crossrefs

Programs

  • Mathematica
    a={1,3,3}; Print[3]; Print[3]; For[n=3, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[sum]]; a=RotateLeft[a]; a[[3]]=sum]

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

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

A249413 Primes in the hexanacci numbers sequence A000383.

Original entry on oeis.org

11, 41, 72426721, 143664401, 565262081, 4160105226881, 253399862985121, 997027328131841, 212479323351825962211841, 188939838859312612896128881921, 22828424707602602744356458636161, 661045104283639247572028952777478721
Offset: 1

Views

Author

Robert Price, Dec 03 2014

Keywords

Comments

a(13) is too large to display here. It has 62 digits and is the 210th term in A000383.

Crossrefs

Programs

  • Mathematica
    a={1,1,1,1,1,1}; For[n=6, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[sum]]; a=RotateLeft[a]; a[[5]]=sum]

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

A247027 Indices of primes in the tetranacci sequence A001631.

Original entry on oeis.org

5, 7, 12, 19, 47, 97, 124, 244, 564, 1037, 12007, 13662, 180039
Offset: 1

Views

Author

Robert Price, Sep 09 2014

Keywords

Comments

a(14) > 2*10^5.

Crossrefs

Programs

  • Mathematica
    a={0,0,1,0}; For[n=4, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[n]]; a=RotateLeft[a]; a[[4]]=sum]

A241660 Indices of primes in A001630.

Original entry on oeis.org

3, 4, 7, 19, 62, 94, 722, 5197, 5262, 6182, 14007, 21579, 35354, 75592
Offset: 1

Views

Author

Robert Price, Apr 26 2014

Keywords

Comments

a(15) > 2*10^5.

Crossrefs

Programs

  • Mathematica
    a={0,0,1,2}; Print[3]; For[n=4, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[n]]; a=RotateLeft[a]; a[[4]]=sum]

Extensions

Prepended a(1)=3 and Mathematica program corrected by Robert Price, Sep 09 2014
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