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 12 results. Next

A068601 a(n) = n^3 - 1.

Original entry on oeis.org

0, 7, 26, 63, 124, 215, 342, 511, 728, 999, 1330, 1727, 2196, 2743, 3374, 4095, 4912, 5831, 6858, 7999, 9260, 10647, 12166, 13823, 15624, 17575, 19682, 21951, 24388, 26999, 29790, 32767, 35936, 39303, 42874, 46655, 50652, 54871, 59318, 63999, 68920
Offset: 1

Views

Author

Naohiro Nomoto, Mar 28 2002

Keywords

Comments

a(n) is the least positive integer k such that k can only contain 'n-1' in exactly 2 different bases B, where 1 < B <= k.
Apart from the first term, the same as A135300. - R. J. Mathar, Apr 29 2008
A058895(n)^3 + a(n)^3 + A033562(n)^3 = A185065(n)^3. - Vincenzo Librandi, Mar 13 2012
Numbers k such that for every nonnegative integer m, k^(3*m+1) + k^(3*m) is a cube. - Arkadiusz Wesolowski, Aug 10 2013

Examples

			For n=6; 215 written in bases 6 and 42 is 555, 55 and (555, 55) are exactly 2 different bases.
		

Crossrefs

Programs

Formula

Partial sums of A003215, hex (or centered hexagonal) numbers: 3*n(n+1)+1. - Jonathan Vos Post, Mar 16 2006
G.f.: x^2*(7-2*x+x^2)/(1-x)^4. - Colin Barker, Feb 12 2012
4*a(m^2-2*m+2) = (m^2-m+1)^3 + (m^2-m-1)^3 + (m^2-3*m+3)^3 + (m^2-3*m+1)^3. - Bruno Berselli, Jun 23 2014
a(n) = Sum_{i=1..n-1} (i+1)^3 - i^3. - Wesley Ivan Hurt, Jul 23 2014
Sum_{n>=2} 1/a(n) = Sum_{n>=1} (zeta(3*n) - 1) = A339604. - Amiram Eldar, Nov 06 2020
Product_{n>=2} (1 + 1/a(n)) = 3*Pi*sech(sqrt(3)*Pi/2). - Amiram Eldar, Jan 20 2021
E.g.f.: 1 + exp(x)*(x^3 + 3*x^2 + x - 1). - Stefano Spezia, Jul 06 2021

A269776 T(n,k)=Number of length-n 0..k arrays with every repeated value unequal to the previous repeated value plus one mod k+1.

Original entry on oeis.org

2, 3, 4, 4, 9, 8, 5, 16, 27, 14, 6, 25, 64, 78, 24, 7, 36, 125, 252, 222, 40, 8, 49, 216, 620, 984, 624, 66, 9, 64, 343, 1290, 3060, 3816, 1740, 108, 10, 81, 512, 2394, 7680, 15040, 14724, 4824, 176, 11, 100, 729, 4088, 16674, 45600, 73680, 56592, 13320, 286, 12, 121
Offset: 1

Views

Author

R. H. Hardin, Mar 04 2016

Keywords

Comments

Table starts
...2.....3......4.......5........6.........7..........8..........9.........10
...4.....9.....16......25.......36........49.........64.........81........100
...8....27.....64.....125......216.......343........512........729.......1000
..14....78....252.....620.....1290......2394.......4088.......6552.......9990
..24...222....984....3060.....7680.....16674......32592......58824......99720
..40...624...3816...15040....45600....115920.....259504.....527616.....994680
..66..1740..14724...73680...270150....804636....2063880....4728384....9915210
.108..4824..56592..360000..1597500...5577768...16398144...42342912...98779500
.176.13320.216864.1755200..9432000..38621016..130175360..378929664..983566800
.286.36672.829116.8542720.55616250.267152256.1032602872.3389054976.9788946390

Examples

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

Crossrefs

Column 1 is A019274(n+2).
Column 2 is A269613.
Row 1 is A000027(n+1).
Row 2 is A000290(n+1).
Row 3 is A000578(n+1).
Row 4 is A058895(n+1).

Formula

Empirical for column k (apparently a(n) = 2*k*a(n-1) -k*(k-1)*a(n-2) -k^2*a(n-3)):
k=1: a(n) = 2*a(n-1) -a(n-3)
k=2: a(n) = 4*a(n-1) -2*a(n-2) -4*a(n-3)
k=3: a(n) = 6*a(n-1) -6*a(n-2) -9*a(n-3)
k=4: a(n) = 8*a(n-1) -12*a(n-2) -16*a(n-3)
k=5: a(n) = 10*a(n-1) -20*a(n-2) -25*a(n-3)
k=6: a(n) = 12*a(n-1) -30*a(n-2) -36*a(n-3)
k=7: a(n) = 14*a(n-1) -42*a(n-2) -49*a(n-3)
Empirical for row n:
n=1: a(n) = n + 1
n=2: a(n) = n^2 + 2*n + 1
n=3: a(n) = n^3 + 3*n^2 + 3*n + 1
n=4: a(n) = n^4 + 4*n^3 + 6*n^2 + 3*n
n=5: a(n) = n^5 + 5*n^4 + 10*n^3 + 7*n^2 + n
n=6: a(n) = n^6 + 6*n^5 + 15*n^4 + 14*n^3 + 4*n^2
n=7: a(n) = n^7 + 7*n^6 + 21*n^5 + 25*n^4 + 11*n^3 + n^2

A284823 Array read by antidiagonals: T(n,k) = number of primitive (aperiodic) palindromes of length n using a maximum of k different symbols (n >= 1, k >= 1).

Original entry on oeis.org

1, 2, 0, 3, 0, 0, 4, 0, 2, 0, 5, 0, 6, 2, 0, 6, 0, 12, 6, 6, 0, 7, 0, 20, 12, 24, 4, 0, 8, 0, 30, 20, 60, 18, 14, 0, 9, 0, 42, 30, 120, 48, 78, 12, 0, 10, 0, 56, 42, 210, 100, 252, 72, 28, 0, 11, 0, 72, 56, 336, 180, 620, 240, 234, 24, 0, 12, 0, 90, 72, 504, 294, 1290, 600, 1008, 216, 62
Offset: 1

Views

Author

Andrew Howroyd, Apr 03 2017

Keywords

Examples

			Table starts:
1  2   3    4    5    6     7     8     9    10 ...
0  0   0    0    0    0     0     0     0     0 ...
0  2   6   12   20   30    42    56    72    90 ...
0  2   6   12   20   30    42    56    72    90 ...
0  6  24   60  120  210   336   504   720   990 ...
0  4  18   48  100  180   294   448   648   900 ...
0 14  78  252  620 1290  2394  4088  6552  9990 ...
0 12  72  240  600 1260  2352  4032  6480  9900 ...
0 28 234 1008 3100 7740 16758 32704 58968 99900 ...
0 24 216  960 3000 7560 16464 32256 58320 99000 ...
...
Row 4 includes palindromes of the form abba but excludes those of the form aaaa, so T(4,k) is k*(k-1).
Row 6 includes palindromes of the forms aabbaa, abbbba, abccba but excludes those of the forms aaaaaa, abaaba, so T(6,k) is 2*k*(k-1) + k*(k-1)*(k-2).
		

References

  • M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

Crossrefs

Columns 2-6 are A056458, A056459, A056460, A056461, A056462.
Rows 5-10 are A007531(k+1), A045991, A058895, A047928(k-1), A135497, A133754.

Programs

  • Mathematica
    T[n_, k_] := DivisorSum[n, MoebiusMu[n/#]*k^Ceiling[#/2]&]; Table[T[n-k+1, k], {n, 1, 12}, {k, n, 1, -1}] // Flatten (* Jean-François Alcover, Jun 05 2017 *)
  • PARI
    a(n,k) = sumdiv(n, d, moebius(n/d) * k^(ceil(d/2)));
    for(n=1, 10, for(k=1, 10, print1( a(n,k),", ");); print();)

Formula

T(n,k) = Sum_{d | n} mu(n/d) * k^(ceiling(d/2)).

A033562 a(n) = 2*n^3 + 1.

Original entry on oeis.org

1, 3, 17, 55, 129, 251, 433, 687, 1025, 1459, 2001, 2663, 3457, 4395, 5489, 6751, 8193, 9827, 11665, 13719, 16001, 18523, 21297, 24335, 27649, 31251, 35153, 39367, 43905, 48779, 54001, 59583, 65537, 71875, 78609, 85751, 93313, 101307, 109745, 118639, 128001
Offset: 0

Views

Author

Keywords

Comments

A058895(n)^3 + A068601(n)^3 + a(n)^3 = A185065(n)^3, for n>0. - Vincenzo Librandi, Mar 13 2012

Crossrefs

Programs

Formula

G.f.: 1 + x*(3 + 5*x + 5*x^2 - x^3)/(1-x)^4. - Vincenzo Librandi, Mar 13 2012
E.g.f.: (1 + 2*x + 6*x^2 + 2*x^3)*exp(x). - G. C. Greubel, Oct 12 2019

Extensions

Terms a(34) onward added by G. C. Greubel, Oct 12 2019

A131471 a(n) = n^5+n.

Original entry on oeis.org

0, 2, 34, 246, 1028, 3130, 7782, 16814, 32776, 59058, 100010, 161062, 248844, 371306, 537838, 759390, 1048592, 1419874, 1889586, 2476118, 3200020, 4084122, 5153654, 6436366, 7962648, 9765650, 11881402, 14348934, 17210396, 20511178, 24300030, 28629182, 33554464
Offset: 0

Views

Author

Mohammad K. Azarian, Jul 27 2007

Keywords

Crossrefs

Programs

Formula

G.f.: 2*x*(1+11*x+36*x^2+11*x^3+x^4)/(-1+x)^6. - R. J. Mathar, Nov 14 2007
a(n) = A271208(n) + 1 = A271209(n) - 1. - Paolo Xausa, Nov 03 2024

A185065 a(n) = n*(n^3 + 2).

Original entry on oeis.org

0, 3, 20, 87, 264, 635, 1308, 2415, 4112, 6579, 10020, 14663, 20760, 28587, 38444, 50655, 65568, 83555, 105012, 130359, 160040, 194523, 234300, 279887, 331824, 390675, 457028, 531495, 614712, 707339, 810060, 923583, 1048640
Offset: 0

Views

Author

Vincenzo Librandi, Mar 31 2011

Keywords

Comments

Numbers a(n) such that a(n)^3 = x^3*(x-2). The values of x are in A084380.
A058895(n)^3 + A068601(n)^3 + A033562(n)^3 = a(n)^3, for n > 0. - Vincenzo Librandi, Mar 13 2012

Examples

			20^3 = 10^3*(10-2); 87^3 = 29^3*(29-2).
		

Crossrefs

Programs

Formula

G.f.: x*(3 + 5*x + 17*x^2 - x^3)/(1-x)^5. - Bruno Berselli, Mar 31 2011

A131472 a(n) = n^6 + n.

Original entry on oeis.org

0, 2, 66, 732, 4100, 15630, 46662, 117656, 262152, 531450, 1000010, 1771572, 2985996, 4826822, 7529550, 11390640, 16777232, 24137586, 34012242, 47045900, 64000020, 85766142, 113379926, 148035912, 191103000, 244140650, 308915802
Offset: 0

Views

Author

Mohammad K. Azarian, Jul 27 2007

Keywords

Crossrefs

Programs

  • Magma
    [n^6+n: n in [0..30]]; // _Vincenzo Librandi+, Oct 01 2011
  • Mathematica
    Table[n^6+n,{n,0,60}] (* Vladimir Joseph Stephan Orlovsky, May 12 2011 *)
    LinearRecurrence[{7,-21,35,-35,21,-7,1},{0,2,66,732,4100,15630,46662},60] (* Harvey P. Dale, May 03 2012 *)

Formula

G.f.: 2*x*(1 + 26*x + 156*x^2 + 146*x^3 + 31*x^4)/(1 - x)^7. - R. J. Mathar, Nov 14 2007
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7); a(0)=0, a(1)=2, a(2)=66, a(3)=732, a(4)=4100, a(5)=15630, a(6)=46662. - Harvey P. Dale, May 03 2012
E.g.f.: exp(x)*x*(2 + 31*x + 90*x^2 + 65*x^3 + 15*x^4 + x^5). - Stefano Spezia, Oct 08 2022

A027482 a(n) = n*(n^3 - 1)/2.

Original entry on oeis.org

7, 39, 126, 310, 645, 1197, 2044, 3276, 4995, 7315, 10362, 14274, 19201, 25305, 32760, 41752, 52479, 65151, 79990, 97230, 117117, 139909, 165876, 195300, 228475, 265707, 307314, 353626, 404985, 461745, 524272, 592944, 668151
Offset: 2

Views

Author

Keywords

Comments

Row sums in an n X n X n pandiagonal magic cube with entries (0..n^3-1).

Crossrefs

First subdiagonal of A027478 (Cube of a triangular matrix constructed from the Stirling numbers of the first kind).

Programs

  • Magma
    [n * (n^3 - 1)/2: n in [2..50]]; // Vincenzo Librandi, Dec 29 2012
  • Mathematica
    Table[(m^4 - m)/2, {m, 44}] (* Zerinvary Lajos, Mar 21 2007 *)
    CoefficientList[Series[(7 + 4*x + x^2)/(1 - x)^5, {x, 0, 40}], x] (* Vincenzo Librandi, Dec 29 2012 *)
  • PARI
    t(n)=n*(n+1)/2;
    for(n=0,50,print1(t(n^2)-t(n)","))
    

Formula

a(n) = A027478(n,n-1)
a(n) = A000217(n^2) - A000217(n). - Jon Perry, Jul 21 2003
a(n) = A058895(n)/2. - Zerinvary Lajos, Jan 28 2008
G.f.: x^2*(7 + 4*x + x^2)/(1 - x)^5. - Vincenzo Librandi, Dec 29 2012
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n > 6. - Chai Wah Wu, Apr 08 2021

A262705 Triangle: Newton expansion of C(n,m)^4, read by rows.

Original entry on oeis.org

1, 0, 1, 0, 14, 1, 0, 36, 78, 1, 0, 24, 978, 252, 1, 0, 0, 4320, 8730, 620, 1, 0, 0, 8460, 103820, 46890, 1290, 1, 0, 0, 7560, 581700, 1159340, 185430, 2394, 1, 0, 0, 2520, 1767360, 13387570, 8314880, 595476, 4088, 1, 0, 0, 0, 3087000, 85806000, 170429490, 44341584, 1642788, 6552, 1
Offset: 0

Views

Author

Giuliano Cabrele, Sep 30 2015

Keywords

Comments

Triangle here T_4(n,m) is such that C(n,m)^4 = Sum_{j=0..n} C(n,j)*T_4(j,m).
Equivalently, lower triangular matrix T_4 such that
|| C(n,m)^4 || = A202750 = P * T_4 = A007318 * T_4.
T_4(n,m) = 0 for n < m and for 4*m < n.
Refer to comment to A262704.
Example:
C(x,2)^4 = x^4*(x-1)^4 /16 = 1*C(x,2) + 78*C(x,3) + 978*C(x,4) + 4320*C(x,5) + 8460*C(x,6) + 7560*C(x,7) + 2520*C(x,8);
C(5,2)^4 = C(5,3)^4 = 10000 = 1*C(5,2) + 78*C(5,3) + 978*C(5,4) + 4320*C(5,5) = 1*C(5,3) + 252*C(5,4) + 8730*C(5,5).

Examples

			Triangle starts:
[1];
[0,  1];
[0, 14,    1];
[0, 36,   78,      1];
[0, 24,  978,    252,     1];
[0,  0, 4320,   8730,   620,    1];
[0,  0, 8460, 103820, 46890, 1290, 1];
		

Crossrefs

Row sums are, by definition, the inverse binomial transform of A005260.
Second diagonal (T_4(n+1,n)) is A058895(n+1).
Column T_4(n,2) is A122193(4,n).
Cf. A109983 (transpose of), A262704, A262706.

Programs

  • Magma
    [&+[(-1)^(n-j)*Binomial(n,j)*Binomial(j,m)^4: j in [0..n]]: m in [0..n], n in [0..10]]; // Bruno Berselli, Oct 01 2015
    
  • Mathematica
    T4[n_, m_] := Sum[(-1)^(n - j) * Binomial[n, j] * Binomial[j, m]^4, {j, 0, n}]; Table[T4[n, m], {n, 0, 9}, {m, 0, n}] // Flatten (* Jean-François Alcover, Oct 01 2015 *)
  • MuPAD
    // as a function
    T_4:=(n,m)->_plus((-1)^(n-j)*binomial(n,j)*binomial(j,m)^4 $ j=0..n):
    // as a matrix h x h
    _P:=h->matrix([[binomial(n,m) $m=0..h]$n=0..h]):
    _P_4:=h->matrix([[binomial(n,m)^4 $m=0..h]$n=0..h]):
    _T_4:=h->_P(h)^-1*_P_4(h):
    
  • PARI
    T_4(nmax) = {for(n=0, nmax, for(m=0, n, print1(sum(j=0, n, (-1)^(n-j)*binomial(n,j)*binomial(j,m)^4), ", ")); print())} \\ Colin Barker, Oct 01 2015

Formula

T_4(n,m) = Sum_{j=0..n} (-1)^(n-j)*C(n,j)*C(j,m)^4.
Also, let S(r,s)(n,m) denote the Generalized Stirling2 numbers as defined in the link above, then T_4(n,m) = n! / (m!)^4 * S(m,m)(4,n).

A131473 a(n) = n^6 - n.

Original entry on oeis.org

0, 0, 62, 726, 4092, 15620, 46650, 117642, 262136, 531432, 999990, 1771550, 2985972, 4826796, 7529522, 11390610, 16777200, 24137552, 34012206, 47045862, 63999980, 85766100, 113379882, 148035866, 191102952, 244140600, 308915750
Offset: 0

Views

Author

Mohammad K. Azarian, Jul 27 2007

Keywords

Crossrefs

Programs

Showing 1-10 of 12 results. Next