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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A152741 13 times triangular numbers.

Original entry on oeis.org

0, 13, 39, 78, 130, 195, 273, 364, 468, 585, 715, 858, 1014, 1183, 1365, 1560, 1768, 1989, 2223, 2470, 2730, 3003, 3289, 3588, 3900, 4225, 4563, 4914, 5278, 5655, 6045, 6448, 6864, 7293, 7735, 8190, 8658, 9139, 9633, 10140, 10660, 11193, 11739, 12298, 12870
Offset: 0

Views

Author

Omar E. Pol, Dec 12 2008

Keywords

Comments

Sequence found by reading the line from 0, in the direction 0, 13,... and the same line from 0, in the direction 0, 39,..., in the square spiral whose vertices are the generalized 15-gonal numbers. - Omar E. Pol, Oct 03 2011
Sum of the numbers from 6n to 7n. - Wesley Ivan Hurt, Dec 22 2015

Crossrefs

Programs

Formula

a(n) = 13*n*(n+1)/2 = 13 * A000217(n).
a(n) = a(n-1)+13*n (with a(0)=0). - Vincenzo Librandi, Nov 26 2010
a(n) = A069126(n+1) - 1. - Omar E. Pol, Oct 03 2011
From Wesley Ivan Hurt, Dec 22 2015: (Start)
G.f.: 13*x/(1-x)^3.
a(n) = 3*a(n-1)-3*a(n-2)+a(n-3) for n>2.
a(n) = Sum_{i=6n..7n} i. (End)
E.g.f.: 13*x*(2+x)*exp(x)/2. - G. C. Greubel, Sep 01 2018
From Amiram Eldar, Feb 21 2023: (Start)
Sum_{n>=1} 1/a(n) = 2/13.
Sum_{n>=1} (-1)^(n+1)/a(n) = (4*log(2) - 2)/13.
Product_{n>=1} (1 - 1/a(n)) = -(13/(2*Pi))*cos(sqrt(21/13)*Pi/2).
Product_{n>=1} (1 + 1/a(n)) = (13/(2*Pi))*cos(sqrt(5/13)*Pi/2). (End)

A195158 Concentric 24-gonal numbers.

Original entry on oeis.org

0, 1, 24, 49, 96, 145, 216, 289, 384, 481, 600, 721, 864, 1009, 1176, 1345, 1536, 1729, 1944, 2161, 2400, 2641, 2904, 3169, 3456, 3745, 4056, 4369, 4704, 5041, 5400, 5761, 6144, 6529, 6936, 7345, 7776, 8209, 8664, 9121, 9600, 10081, 10584, 11089
Offset: 0

Views

Author

Omar E. Pol, Sep 28 2011

Keywords

Comments

Sequence found by reading the line from 0, in the direction 0, 24, ..., and the same line from 1, in the direction 1, 49, ..., in the square spiral whose vertices are the generalized tetradecagonal numbers A195818. Main axis, perpendicular to A049598 in the same spiral.

Crossrefs

Column 24 of A195040.

Programs

Formula

a(n) = 6*n^2 + 5*((-1)^n-1)/2.
a(n) = -a(n-1) + A069190(n). - Vincenzo Librandi, Sep 30 2011
From Colin Barker, Sep 16 2012: (Start)
a(n) = 2*a(n-1) - 2*a(n-3) + a(n-4).
G.f.: x*(1+22*x+x^2)/((1-x)^3*(1+x)). (End)
Sum_{n>=1} 1/a(n) = Pi^2/144 + tan(sqrt(5/6)*Pi/2)*Pi/(4*sqrt(30)). - Amiram Eldar, Jan 17 2023

A263226 a(n) = 15*n^2 - 13*n.

Original entry on oeis.org

0, 2, 34, 96, 188, 310, 462, 644, 856, 1098, 1370, 1672, 2004, 2366, 2758, 3180, 3632, 4114, 4626, 5168, 5740, 6342, 6974, 7636, 8328, 9050, 9802, 10584, 11396, 12238, 13110, 14012, 14944, 15906, 16898, 17920, 18972, 20054, 21166, 22308, 23480, 24682, 25914
Offset: 0

Views

Author

Emeric Deutsch, Oct 12 2015

Keywords

Comments

For n>=3, a(n) = the Wiener index of the Jahangir graph J_{3,n}. The Jahangir graph J_{3,n} is a connected graph consisting of a cycle graph C(3n) and one additional center vertex that is adjacent to n vertices of C(3n) at distances 3 to each other on C(3n).
The Hosoya polynomial of J_(3,n) is 4nx + (1/2)n(n+9)x^2 + 2n(n-1)x^3 + n(2n-5)x^4.

Crossrefs

Programs

  • Magma
    [15*n^2-13*n: n in [0..50]]; // Bruno Berselli, Oct 15 2015
  • Maple
    seq(15*n^2-13*n, n = 0 .. 40);
  • Mathematica
    Table[15 n^2 - 13 n, {n, 0, 40}] (* Vincenzo Librandi, Oct 13 2015 *)
    LinearRecurrence[{3,-3,1},{0,2,34},50] (* Harvey P. Dale, Jul 27 2018 *)
  • PARI
    vector(50, n, n--; 15*n^2 - 13*n) \\ Altug Alkan, Oct 12 2015
    

Formula

G.f.: 2*x*(1 + 14*x)/(1 - x)^3. - Vincenzo Librandi, Oct 13 2015
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Vincenzo Librandi, Oct 13 2015

A263227 a(n) = n*(67*n - 89)/2.

Original entry on oeis.org

0, -11, 45, 168, 358, 615, 939, 1330, 1788, 2313, 2905, 3564, 4290, 5083, 5943, 6870, 7864, 8925, 10053, 11248, 12510, 13839, 15235, 16698, 18228, 19825, 21489, 23220, 25018, 26883, 28815, 30814, 32880, 35013, 37213, 39480, 41814, 44215, 46683, 49218, 51820
Offset: 0

Views

Author

Emeric Deutsch, Oct 12 2015

Keywords

Comments

For n>=3, a(n) = the hyper-Wiener index of the Jahangir graph J_{3,n}. The Jahangir graph J_{3,n} is a connected graph consisting of a cycle graph C(3n) and one additional center vertex that is adjacent to n vertices of C(3n) at distances 3 to each other on C(3n).
The Hosoya polynomial of J_(3,n) is 4nx + (1/2)n(n+9)x^2 + 2n(n-1)x^3 + n(2n-5)x^4.

Crossrefs

Programs

  • Magma
    [n*(67*n-89)/2: n in [0..40]]; // Bruno Berselli, Oct 15 2015
  • Maple
    seq((1/2)*n*(67*n-89), n = 0 .. 40);
  • Mathematica
    Table[n (67 n - 89)/2, {n, 0, 40}] (* Vincenzo Librandi, Oct 13 2015 *)
  • PARI
    vector(50, n, n--; n*(67*n-89)/2) \\ Altug Alkan, Oct 12 2015
    

Formula

G.f.: x*(-11+78*x)/(1-x)^3. - Vincenzo Librandi, Oct 13 2015
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Vincenzo Librandi, Oct 13 2015

A263228 a(n) = 2*n*(16*n - 13).

Original entry on oeis.org

0, 6, 76, 210, 408, 670, 996, 1386, 1840, 2358, 2940, 3586, 4296, 5070, 5908, 6810, 7776, 8806, 9900, 11058, 12280, 13566, 14916, 16330, 17808, 19350, 20956, 22626, 24360, 26158, 28020, 29946, 31936, 33990, 36108, 38290, 40536, 42846, 45220, 47658, 50160
Offset: 0

Views

Author

Emeric Deutsch, Oct 13 2015

Keywords

Comments

For n>=3, a(n) = the Wiener index of the Jahangir graph J_{4,n}. The Jahangir graph J_{4,n} is a connected graph consisting of a cycle graph C(4*n) and one additional center vertex that is adjacent to n vertices of C(4*n) at distances 4 to each other on C(4*n). In the Farahani reference the expression in Theorem 2 is accidentally incorrect; it should be 2*m*(16*m - 13).
The Hosoya polynomial of J_{4,n} is 5*n*x + n*(n+11)*x^2/2 + n*(2*n+1)*x^3 + n*(3*n-4)*x^4 + 2*n*(n-2)*x^5 + n*(n-3)*x^6/2 (see the Farahani reference, p. 234, last line; however, the expression in Theorem 1, p. 233, is accidentally incorrect).

Crossrefs

Programs

  • Magma
    [2*n*(16*n-13): n in [0..60]]; // Vincenzo Librandi, Oct 15 2015
    
  • Maple
    seq(32*n^2 - 26*n, n=0..40);
  • Mathematica
    Table[2 n (16 n - 13), {n, 0, 40}] (* Bruno Berselli, Oct 15 2015 *)
  • PARI
    vector(50, n, n--; 2*n*(16*n-13)) \\ Altug Alkan, Oct 15 2015

Formula

G.f.: 2*x*(3+29*x)/(1-x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).

A263229 a(n) = 4*n*(21*n - 26).

Original entry on oeis.org

0, -20, 128, 444, 928, 1580, 2400, 3388, 4544, 5868, 7360, 9020, 10848, 12844, 15008, 17340, 19840, 22508, 25344, 28348, 31520, 34860, 38368, 42044, 45888, 49900, 54080, 58428, 62944, 67628, 72480, 77500, 82688, 88044, 93568, 99260, 105120, 111148, 117344, 123708, 130240
Offset: 0

Views

Author

Emeric Deutsch, Oct 13 2015

Keywords

Comments

For n>=3, a(n) = the hyper-Wiener index of the Jahangir graph J_{4,n}.
See A263228 for more comments.

Crossrefs

Programs

  • Magma
    [4*n*(21*n-26): n in [0..20]]; // Vincenzo Librandi, Oct 15 2015
    
  • Maple
    seq(84*n^2 - 104*n, n=0..40);
  • Mathematica
    Table[4 n (21 n - 26), {n, 0, 40}] (* Bruno Berselli, Oct 15 2015 *)
  • PARI
    vector(50, n, n--; 4*n*(21*n-26)) \\ Altug Alkan, Oct 15 2015

Formula

G.f.: 4*x*(47*x-5)/(1-x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).

A221912 Partial sums of floor(n/12).

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 76, 80, 84, 88, 92, 96, 100, 104, 108, 112, 116, 120, 125, 130, 135, 140, 145, 150, 155
Offset: 0

Views

Author

Philippe Deléham, Mar 27 2013

Keywords

Comments

Apart from the initial zeros, the same as A008730.

Examples

			..0....0....0....0....0....0....0....0....0....0....0....0
..1....2....3....4....5....6....7....8....9...10...11...12
.14...16...18...20...22...24...26...28...30...32...34...36
.39...42...45...48...51...54...57...60...63...66...69...72
.76...80...84...88...92...96..100..104..108..112..116..120
125..130..135..140..145..150..155..160..165..170..175..180
186..192..198..204..210..216..222..228..234..240..246..252
259..266..273..280..287..294..301..308..315..322..329..336
344..352..360..368..376..384..392..400..408..416..424..432
441..450..459..468..477..486..495..504..513..522..531..540
...
		

Crossrefs

Programs

  • Mathematica
    Accumulate[Floor[Range[0,70]/12]] (* or *) LinearRecurrence[{2,-1,0,0,0,0,0,0,0,0,0,1,-2,1},{0,0,0,0,0,0,0,0,0,0,0,0,1,2},70] (* Harvey P. Dale, Mar 23 2015 *)

Formula

a(12n) = A051866(n).
a(12n+1) = A139267(n).
a(12n+2) = A094159(n).
a(12n+3) = A033579(n).
a(12n+4) = A049452(n).
a(12n+5) = A033581(n).
a(12n+6) = A049453(n).
a(12n+7) = A033580(n).
a(12n+8) = A195319(n).
a(12n+9) = A202804(n).
a(12n+10) = A211014(n).
a(12n+11) = A049598(n).
G.f.: x^12/((1-x)^2*(1-x^12)).
a(0)=0, a(1)=0, a(2)=0, a(3)=0, a(4)=0, a(5)=0, a(6)=0, a(7)=0, a(8)=0, a(9)=0, a(10)=0, a(11)=0, a(12)=1, a(13)=2, a(n)=2*a(n-1)- a(n-2)+ a(n-12)- 2*a(n-13)+ a(n-14). - Harvey P. Dale, Mar 23 2015

A008730 Molien series 1/((1-x)^2*(1-x^12)) for 3-dimensional group [2,n] = *22n.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 76, 80, 84, 88, 92, 96, 100, 104, 108, 112, 116, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 186, 192, 198, 204
Offset: 0

Views

Author

Keywords

Examples

			..1....2....3....4....5....6....7....8....9...10...11...12
.14...16...18...20...22...24...26...28...30...32...34...36
.39...42...45...48...51...54...57...60...63...66...69...72
.76...80...84...88...92...96..100..104..108..112..116..120
125..130..135..140..145..150..155..160..165..170..175..180
186..192..198..204..210..216..222..228..234..240..246..252
259..266..273..280..287..294..301..308..315..322..329..336
344..352..360..368..376..384..392..400..408..416..424..432
441..450..459..468..477..486..495..504..513..522..531..540
550..560..570..580..590..600..610..620..630..640..650..660
...
The columns are: A051866, A139267, A094159, A033579, A049452, A033581, A049453, A033580, A195319, A202804, A211014, A049598
- _Philippe Deléham_, Apr 03 2013
		

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 70); Coefficients(R!( 1/((1-x)^2*(1-x^12)) )); // G. C. Greubel, Jul 30 2019
    
  • Maple
    seq(coeff(series(1/(1-x)^2/(1-x^12), x, n+1), x, n), n=0..80);
  • Mathematica
    CoefficientList[Series[1/((1-x)^2*(1-x^12)), {x,0,70}], x] (* Vincenzo Librandi, Jun 11 2013 *)
    LinearRecurrence[{2,-1,0,0,0,0,0,0,0,0,0,1,-2,1},{1,2,3,4,5,6,7,8,9,10,11,12,14,16},70] (* Harvey P. Dale, Jan 01 2024 *)
  • PARI
    my(x='x+O('x^70)); Vec(1/((1-x)^2*(1-x^12))) \\ G. C. Greubel, Jul 30 2019
    
  • Sage
    (1/((1-x)^2*(1-x^12))).series(x, 70).coefficients(x, sparse=False) # G. C. Greubel, Jul 30 2019

Formula

G.f. 1/( (1-x)^3 * (1+x) *(1+x+x^2) *(1-x+x^2) * (1+x^2) *(1-x^2+x^4)). - R. J. Mathar, Aug 11 2021
From Mitch Harris, Sep 08 2008: (Start)
a(n) = Sum_{j=0..n+12} floor(j/12).
a(n-12) = (1/2)*floor(n/12)*(2*n - 10 - 12*floor(n/12)). (End)
a(n) = A221912(n+12). - Philippe Deléham, Apr 03 2013

Extensions

More terms from Vladimir Joseph Stephan Orlovsky, Mar 14 2010

A060834 a(n) = 6*n^2 + 6*n + 31.

Original entry on oeis.org

31, 43, 67, 103, 151, 211, 283, 367, 463, 571, 691, 823, 967, 1123, 1291, 1471, 1663, 1867, 2083, 2311, 2551, 2803, 3067, 3343, 3631, 3931, 4243, 4567, 4903, 5251, 5611, 5983, 6367, 6763, 7171, 7591, 8023, 8467, 8923, 9391, 9871, 10363, 10867, 11383
Offset: 0

Views

Author

Jason Earls, May 02 2001

Keywords

Comments

First 29 values are primes.
From Peter Bala, Apr 18 2018: (Start)
Let P(n) = 6*n^2 + 6*n + 31. The polynomial P(2*n-14) = 24*n^2 - 660*n + 4567 takes distinct prime values for n = 0 to 28.
The value of the polynomial 2*P(3/2*(n-10)) = 27*n^2 - 522*n + 2582 for n = 0 to 22 is either double a prime or a prime (alternately).
The value of the polynomial 4*P(4/3*(n-9)) = 32*n^2 - 552*n + 2469 for n = 0 to 28 is either prime or 3 times a prime, except when n = 16. (End)
Also, numbers k such that 2*k/3 - 2/3 - 19 is a perfect square. - Bruno Berselli, Apr 23 2018
Equivalently, numbers k such that 6*k - 177 is a square. - Vincenzo Librandi, Apr 23 2018

Examples

			a(29)=4903, prime. a(30)=5251, nonprime.
		

References

  • Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag NY 2004. See p. 145.
  • Donald D. Spencer, Computers in Number Theory, Computer Science Press, Rockville, MD, 1982, pp. 118-119.

Crossrefs

Programs

  • GAP
    List([0..80],n->6*n^2+6*n+31); # Muniru A Asiru, Apr 22 2018
  • Mathematica
    Table[6n^2+6n+31,{n,0,60}] (* or *) LinearRecurrence[{3,-3,1},{31,43,67},60] (* Harvey P. Dale, Aug 09 2011 *)
  • PARI
    a(n) = { 6*n^2 + 6*n + 31 } \\ Harry J. Smith, Jul 19 2009
    

Formula

From R. J. Mathar, Feb 05 2008: (Start)
O.g.f.: -(31-50*x+31*x^2)/(-1+x)^3.
a(n) = A049598(n)+31. (End)
a(0)=31, a(1)=43, a(2)=67, a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Harvey P. Dale, Aug 09 2011
E.g.f.: exp(x)*(31 + 12*x + 6*x^2). - Stefano Spezia, Dec 26 2024

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), May 07 2001

A272975 Numbers that are congruent to {0,7} mod 12.

Original entry on oeis.org

0, 7, 12, 19, 24, 31, 36, 43, 48, 55, 60, 67, 72, 79, 84, 91, 96, 103, 108, 115, 120, 127, 132, 139, 144, 151, 156, 163, 168, 175, 180, 187, 192, 199, 204, 211, 216, 223, 228, 235, 240, 247, 252, 259, 264, 271, 276, 283, 288, 295, 300, 307, 312, 319, 324
Offset: 1

Views

Author

Wesley Ivan Hurt, May 30 2016

Keywords

Comments

Numbers that are not congruent to {1, 2, 3, 4, 5, 6, 8, 9, 10, 11} mod 12.
Bisection of A083032.

Crossrefs

Programs

  • Magma
    [n : n in [0..400] | n mod 12 in [0, 7]];
    
  • Maple
    A272975:=n->(12*n-11+(-1)^n)/2: seq(A272975(n), n=1..100);
  • Mathematica
    Table[(12n - 11 + (-1)^n)/2, {n, 80}]
  • PARI
    concat(0, Vec(x^2*(7+5*x)/((x-1)^2*(x+1)) + O(x^99))) \\ Altug Alkan, May 31 2016

Formula

G.f.: x^2*(7+5*x) / ((x-1)^2*(x+1)).
a(n) = a(n-1) + a(n-2) - a(n-3) for n>3.
a(n) = (12*n - 11 + (-1)^n)/2.
a(2k) = A017605(k-1) k>0, a(2k-1) = A008594(k-1) k>0, a(2k)-a(2k-1) = 7.
a(n)-a(-n) = A008594(n) for n>0.
Sum_{i=1..n} a(2*i) = A049453(n) for n>0.
Sum_{i=1..n} a(2*i-1) = A049598(n-1) for n>0.
E.g.f.: 5 + ((12*x - 11)*exp(x) + exp(-x))/2. - David Lovler, Sep 04 2022
Sum_{n>=2} (-1)^n/a(n) = log(2)/4 + log(3)/8 - ((sqrt(3)-1)*Pi + 2*(sqrt(3)+3)*log(sqrt(3)+2))/(24*(sqrt(3)+1)). - Amiram Eldar, Sep 17 2023
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