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.

Previous Showing 11-15 of 15 results.

A151636 Number of permutations of 3 indistinguishable copies of 1..n with exactly 6 adjacent element pairs in decreasing order.

Original entry on oeis.org

0, 0, 1, 49682, 58571184, 21475242671, 4476844162434, 678770257169016, 84698452637705746, 9324662905839457490, 944619860914428706035, 90435965482528402360106, 8327298182652856026223632, 746238093776109096993716949, 65611401726068220422014371676
Offset: 1

Views

Author

R. H. Hardin, May 29 2009

Keywords

Crossrefs

Column k=6 of A174266.

Programs

  • Mathematica
    T[n_, k_]:= T[n, k]= Sum[(-1)^(k-j)*Binomial[3*n+1, k-j+2]*(Binomial[j+1,3])^n, {j, 0, k+2}];
    Table[T[n, 6], {n, 30}] (* G. C. Greubel, Mar 26 2022 *)
  • PARI
    a(n) = sum(j=0, 8, (-1)^j*binomial(3*n+1, 8-j)*(binomial(j+1, 3))^n); \\ Michel Marcus, Mar 27 2022
  • Sage
    @CachedFunction
    def T(n, k): return sum( (-1)^(k-j)*binomial(3*n+1, k-j+2)*(binomial(j+1,3))^n for j in (0..k+2) )
    [T(n, 6) for n in (1..30)] # G. C. Greubel, Mar 26 2022
    

Formula

a(n) = Sum_{j=0..8} (-1)^j*binomial(3*n+1, 8-j)*(binomial(j+1, 3))^n. - G. C. Greubel, Mar 26 2022

Extensions

Terms a(9) and beyond from Andrew Howroyd, May 06 2020

A151637 Number of permutations of 3 indistinguishable copies of 1..n with exactly 7 adjacent element pairs in decreasing order.

Original entry on oeis.org

0, 0, 0, 6750, 40241088, 40396577931, 18096792917796, 5183615502649800, 1129236431002624116, 205937718403143468690, 33309411205799991188160, 4957409194925592040479126, 695659299332984273417824080, 93590807522941640152432361025, 12213007949715545409829962783732
Offset: 1

Views

Author

R. H. Hardin, May 29 2009

Keywords

Crossrefs

Column k=7 of A174266.

Programs

  • Mathematica
    T[n_, k_]:= T[n, k]= Sum[(-1)^(k-j)*Binomial[3*n+1, k-j+2]*(Binomial[j+1,3])^n, {j, 0, k+2}];
    Table[T[n, 7], {n, 30}] (* G. C. Greubel, Mar 26 2022 *)
  • Sage
    @CachedFunction
    def T(n, k): return sum( (-1)^(k-j)*binomial(3*n+1, k-j+2)*(binomial(j+1,3))^n for j in (0..k+2) )
    [T(n, 7) for n in (1..30)] # G. C. Greubel, Mar 26 2022

Formula

a(n) = Sum_{j=0..9} (-1)^(j+1)*binomial(3*n+1, 9-j)*(binomial(j+1, 3))^n. - G. C. Greubel, Mar 26 2022

Extensions

Terms a(9) and beyond from Andrew Howroyd, May 06 2020

A151638 Number of permutations of 3 indistinguishable copies of 1..n with exactly 8 adjacent element pairs in decreasing order.

Original entry on oeis.org

0, 0, 0, 243, 12750255, 40396577931, 41106807537048, 22745757394235250, 8699569720553953791, 2617057246555282014495, 668634213456480163469985, 152325974081288304581227794, 31960987230978975148286275260, 6315174416665212479526100114476
Offset: 1

Views

Author

R. H. Hardin, May 29 2009

Keywords

Crossrefs

Column k=8 of A174266.

Programs

  • Mathematica
    T[n_, k_]:= T[n, k]= Sum[(-1)^(k-j)*Binomial[3*n+1, k-j+2]*(Binomial[j+1,3])^n, {j, 0, k+2}];
    Table[T[n, 8], {n, 30}] (* G. C. Greubel, Mar 26 2022 *)
  • PARI
    a(n) = sum(j=0, 10, (-1)^j*binomial(3*n+1, 10-j)*(binomial(j+1, 3))^n); \\ Michel Marcus, Mar 27 2022
  • Sage
    @CachedFunction
    def T(n, k): return sum( (-1)^(k-j)*binomial(3*n+1, k-j+2)*(binomial(j+1,3))^n for j in (0..k+2) )
    [T(n, 8) for n in (1..30)] # G. C. Greubel, Mar 26 2022
    

Formula

a(n) = Sum_{j=0..10} (-1)^j*binomial(3*n+1, 10-j)*(binomial(j+1, 3))^n. - G. C. Greubel, Mar 26 2022

Extensions

Terms a(9) and beyond from Andrew Howroyd, May 06 2020

A151639 Number of permutations of 3 indistinguishable copies of 1..n with exactly 9 adjacent element pairs in decreasing order.

Original entry on oeis.org

0, 0, 0, 1, 1722320, 21475242671, 53885342499340, 59751188387945950, 40765121565728774056, 20317575263352346466495, 8176401371550779497913310, 2829198944755856389638829950, 877500019282729363773560673680, 251039391334595768636642931100892
Offset: 1

Views

Author

R. H. Hardin, May 29 2009

Keywords

Crossrefs

Column k=9 of A174266.

Programs

  • Mathematica
    T[n_, k_]:= T[n, k]= Sum[(-1)^(k-j)*Binomial[3*n+1, k-j+2]*(Binomial[j+1,3])^n, {j, 0, k+2}];
    Table[T[n, 9], {n, 30}] (* G. C. Greubel, Mar 26 2022 *)
  • Sage
    @CachedFunction
    def T(n, k): return sum( (-1)^(k-j)*binomial(3*n+1, k-j+2)*(binomial(j+1,3))^n for j in (0..k+2) )
    [T(n, 9) for n in (1..30)] # G. C. Greubel, Mar 26 2022

Formula

a(n) = Sum_{j=0..11} (-1)^(j+1)*binomial(3*n+1, 11-j)*(binomial(j+1, 3))^n. - G. C. Greubel, Mar 26 2022

Extensions

Terms a(9) and beyond from Andrew Howroyd, May 06 2020

A289254 a(n) = 4^n - 3*n - 1.

Original entry on oeis.org

0, 9, 54, 243, 1008, 4077, 16362, 65511, 262116, 1048545, 4194270, 16777179, 67108824, 268435413, 1073741778, 4294967247, 17179869132, 68719476681, 274877906886, 1099511627715, 4398046511040, 17592186044349, 70368744177594, 281474976710583, 1125899906842548
Offset: 1

Views

Author

Eric W. Weisstein, Jun 29 2017

Keywords

Comments

Number of connected dominating sets in the n-cocktail party graph.

Crossrefs

Column 1 of A174266.

Programs

  • Magma
    [4^n -(3*n+1): n in [1..30]]; // G. C. Greubel, Mar 26 2022
    
  • Mathematica
    Table[4^n - 3 n - 1, {n, 20}]
    LinearRecurrence[{6, -9, 4}, {0, 9, 54}, 20]
    CoefficientList[Series[-((9 x)/((-1 + x)^2 (-1 + 4 x))), {x, 0, 20}], x]
  • PARI
    concat(0, Vec(9*x^2 / ((1 - x)^2*(1 - 4*x)) + O(x^30))) \\ Colin Barker, Jun 30 2017
    
  • Sage
    [4^n -(3*n+1) for n in (1..30)] # G. C. Greubel, Mar 26 2022

Formula

a(n) = 4^n - 3*n - 1.
a(n) = 6*a(n-1) - 9*a(n-2) + 4*a(n-2).
G.f.: 9*x^2/((1-x)^2*(1-4*x)).
E.g.f.: exp(4*x) - (1+3*x)*exp(x). - G. C. Greubel, Mar 26 2022
Previous Showing 11-15 of 15 results.