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 1-4 of 4 results.

A342167 a(n) = U(n, (n+2)/2) where U(n, x) is a Chebyshev polynomial of the 2nd kind.

Original entry on oeis.org

1, 3, 15, 115, 1189, 15456, 242047, 4435929, 93149001, 2205405829, 58130412911, 1688353631328, 53577891882061, 1844491975179855, 68470281953483775, 2726406212682669391, 115921586524134874897, 5241862216131004082160, 251197634537351883217999
Offset: 0

Views

Author

Seiichi Manyama, Mar 03 2021

Keywords

Crossrefs

Programs

  • Mathematica
    Table[ChebyshevU[n, (n + 2)/2], {n, 0, 18}] (* Amiram Eldar, Apr 27 2021 *)
  • PARI
    a(n) = polchebyshev(n, 2, (n+2)/2);
    
  • PARI
    a(n) = sum(k=0, n, n^(n-k)*binomial(2*n+1-k, k));
    
  • PARI
    a(n) = sum(k=0, n, n^k*binomial(n+1+k, 2*k+1));

Formula

a(n) = Sum_{k=0..n} n^(n-k) * binomial(2*n+1-k,k) = Sum_{k=0..n} n^k * binomial(n+1+k,2*k+1).
a(n) ~ exp(2) * n^n. - Vaclav Kotesovec, May 06 2021

A372817 Table read by antidiagonals: T(m,n) = number of 1-metered (m,n)-parking functions.

Original entry on oeis.org

1, 0, 2, 0, 3, 3, 0, 4, 8, 4, 0, 6, 21, 15, 5, 0, 8, 55, 56, 24, 6, 0, 12, 145, 209, 115, 35, 7, 0, 16, 380, 780, 551, 204, 48, 8, 0, 24, 1000, 2912, 2640, 1189, 329, 63, 9, 0, 32, 2625, 10868, 12649, 6930, 2255, 496, 80, 10, 0, 48, 6900, 40569, 60606, 40391, 15456, 3905, 711, 99, 11
Offset: 1

Views

Author

Spencer Daugherty, May 13 2024

Keywords

Examples

			For T(3,2) the 1-metered (3,2)-parking functions are 111, 121, 211, 212.
Table begins:
  1,  2,    3,     4,     5,      6,      7, ...
  0,  3,    8,    15,    24,     35,     48, ...
  0,  4,   21,    56,   115,    204,    329, ...
  0,  6,   55,   209,   551,   1189,   2255, ...
  0,  8,  145,   780,  2640,   6930,  15456, ...
  0, 12,  380,  2912, 12649,  40391, 105937, ...
  0, 16, 1000, 10868, 60606, 235416, 726103, ...
  ...
		

Crossrefs

Main diagonal is A097690 and first row of A372816.
First, second, and third diagonals above main are A097691, A342167, A342168.
Second column A029744. Second row A005563. Third row A242135.

Formula

T(m,n) = (n*(n+sqrt(n^2 - 4))-2)/(n*(n+sqrt(n^2 - 4))-4)*((n+sqrt(n^2-4))/2)^m + (n*(n-sqrt(n^2 - 4))-2)/(n*(n-sqrt(n^2 - 4))-4)*((n-sqrt(n^2-4))/2)^m.
T(m,n) = n*T(m-1,n) - T(m-2,n) with T(0,n) = 1.

A342207 a(n) = U(n,n+1) where U(n,x) is a Chebyshev polynomial of the second kind.

Original entry on oeis.org

1, 4, 35, 496, 9701, 241956, 7338631, 262184896, 10783446409, 501827040100, 26069206375211, 1495427735314800, 93885489910449901, 6403169506981578436, 471427031236487965199, 37265225545829174607616, 3147895910861898495432209
Offset: 0

Views

Author

Seiichi Manyama, Mar 05 2021

Keywords

Crossrefs

Programs

  • Mathematica
    Table[ChebyshevU[n, n + 1], {n, 0, 16}] (* Amiram Eldar, Mar 05 2021 *)
  • PARI
    a(n) = polchebyshev(n, 2, n+1);
    
  • PARI
    a(n) = sum(k=0, n, (2*n)^(n-k)*binomial(2*n+1-k, k));
    
  • PARI
    a(n) = sum(k=0, n, (2*n)^k*binomial(n+1+k, 2*k+1));

Formula

a(n) = Sum_{k=0..n} (2*n)^(n-k) * binomial(2*n+1-k,k) = Sum_{k=0..n} (2*n)^k * binomial(n+1+k,2*k+1).
a(n) ~ exp(1) * 2^n * n^n. - Vaclav Kotesovec, Mar 05 2021

A384162 Number of length n words over an n-ary alphabet such that a single letter in every run of letters is marked.

Original entry on oeis.org

1, 6, 45, 460, 5945, 92736, 1694329, 35487432, 838341009, 22054058290, 639434542021, 20260243575936, 696512594466793, 25822887652517970, 1027054229302256625, 43622499402922710256, 1970666970910292873249, 94353519890358073478880, 4772755056209685781141981
Offset: 1

Views

Author

John Tyler Rascoe, May 21 2025

Keywords

Examples

			a(2) = 6 counts: (1#,1), (1,1#), (1#,2#), (2#,1#), (2#,2), (2,2#) where # denotes a mark.
		

Crossrefs

Programs

  • PARI
    a(n) = concat([0],Vec(n*x/(1-x*(1-x+n))+O('x^(n+1))))[n+1]

Formula

a(n) = [x^n] n*x/(1 - x*(1 - x + n)).
a(n) = Sum_{s} Product_{i=1..k} c_i * (n - 1 + [i,1]) where the sum is over all compositions of n, [c_1, c_2, ..., c_k].
Conjecture: a(n) = n * A342168(n-1).
Showing 1-4 of 4 results.