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 1-5 of 5 results.

A081369 Binomial(n^2, n) reduced mod n^2.

Original entry on oeis.org

0, 2, 3, 12, 5, 12, 7, 56, 9, 40, 11, 108, 13, 84, 90, 240, 17, 144, 19, 80, 315, 220, 23, 72, 25, 312, 27, 560, 29, 0, 31, 992, 759, 544, 770, 720, 37, 684, 1053, 520, 41, 252, 43, 1408, 1125, 1012, 47, 1872, 49, 1200, 918, 624, 53, 1404, 2475, 2744, 2223, 1624, 59
Offset: 1

Views

Author

Labos Elemer, Mar 20 2003

Keywords

Crossrefs

Programs

Formula

a(n)=Mod[C(n^2, n), n^2]

A080216 a(n) is the largest value taken by binomial(n,j) mod j for j in [1..n].

Original entry on oeis.org

0, 1, 1, 1, 1, 3, 3, 4, 2, 5, 5, 7, 7, 7, 11, 8, 8, 9, 9, 13, 16, 11, 11, 15, 15, 13, 21, 18, 18, 18, 18, 18, 26, 26, 21, 25, 25, 21, 31, 28, 28, 29, 29, 31, 39, 27, 27, 36, 34, 31, 41, 34, 34, 45, 45, 36, 46, 46, 46, 43, 43, 41, 51, 40, 48, 52, 52, 52, 56, 44, 44, 52, 52, 57, 61
Offset: 1

Views

Author

Labos Elemer, Mar 21 2003

Keywords

Examples

			n=13: {binomial(13,j) mod j, j=1..13} = {0,0,1,3,2,0,1,7,4,6,1,1,1}; maximum is 7, so a(13) = 7.
		

Crossrefs

Programs

  • Mathematica
    Table[Max[Table[Mod[Binomial[n, j], j], {j, 1, n}]], {n, 1, 256}]
  • PARI
    a(n) = vecmax(vector(n, j, binomial(n, j) % j)); \\ Michel Marcus, Jul 29 2017
    
  • Sage
    def a(n):
        return max([binomial(n,j)%j for j in range(1, n+1)])  # Robin Visser, Nov 26 2023

Formula

a(n) = max_{j=1..n} binomial(n,j) mod j.

A080217 a(n) is the number of distinct values taken by binomial(n,j) mod j for j in [1..n].

Original entry on oeis.org

1, 2, 2, 2, 2, 4, 4, 4, 3, 4, 4, 7, 7, 6, 5, 7, 7, 7, 7, 9, 11, 12, 12, 12, 11, 11, 10, 11, 11, 12, 12, 12, 11, 12, 12, 13, 13, 13, 17, 18, 18, 15, 15, 18, 21, 17, 17, 19, 19, 18, 17, 16, 16, 20, 20, 23, 25, 23, 23, 26, 26, 24, 22, 24, 24, 27, 27, 27, 25, 28, 28, 30, 30, 32, 31, 30
Offset: 1

Views

Author

Labos Elemer, Mar 21 2003

Keywords

Examples

			n=14: {binomial(14,j) mod j, j=1..14} = {0,1,1,1,2,3,2,3,4,1,1,7,1,1} includes six distinct residues (0,1,2,3,4,7) so a(14) = 6.
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Union[Table[Mod[Binomial[n, j], j], {j, 1, n}]]], {n, 1, 256}]
  • PARI
    a(n) = #vecsort(vector(n, j, binomial(n, j) % j), ,8); \\ Michel Marcus, Jul 29 2017
    
  • Sage
    def a(n):
        return len(set([binomial(n,j)%j for j in range(1, n+1)]))  # Robin Visser, Nov 26 2023

Formula

a(n) = Card(Union{j=1..n} binomial(n,j) mod j).

A371472 Least positive number k such that binomial(k^2,k) is divisible by n^2.

Original entry on oeis.org

1, 3, 8, 6, 9, 8, 10, 23, 16, 16, 16, 14, 23, 10, 9, 23, 45, 16, 27, 16, 34, 16, 33, 23, 94, 23, 105, 20, 77, 16, 54, 91, 16, 45, 19, 16, 83, 27, 23, 30, 58, 34, 114, 16, 16, 40, 133, 23, 130, 94, 45, 23, 75, 105, 16, 38, 27, 77, 145, 16, 106, 54, 47, 91, 49, 16, 190, 45, 80, 19, 123, 47, 283, 83, 94, 27, 40, 23, 137
Offset: 1

Views

Author

Seiichi Manyama, Mar 24 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = my(k=1); while(binomial(k^2, k)%n^2>0, k++); k;

A371474 Numbers k such that binomial(k^2,k) == 0 (mod k^3).

Original entry on oeis.org

1, 2184, 6552, 12870, 13860, 19530, 23100, 33660, 40755, 47880, 51051, 58995, 81396, 88920, 101010, 113553, 114114, 114855, 121800, 125970, 136136, 141372, 142290, 142324, 145860, 150535, 154583, 157080, 158928, 164424, 171080, 180180, 193732, 195104, 197340, 214890, 225680, 229908, 230230, 230724, 238602, 243542, 249964, 253080, 257712, 267960, 284867, 291720, 294525, 297414, 300696
Offset: 1

Views

Author

Seiichi Manyama, Mar 24 2024

Keywords

Crossrefs

Programs

  • PARI
    isok(n) = binomial(n^2, n)%n^3==0;
    
  • Python
    from itertools import count, islice
    from math import comb
    def A371474_gen(): # generator of terms
        return filter(lambda k:not comb(k**2,k)%(k**3),count(1))
    A371474_list = list(islice(A371474_gen(),3)) # Chai Wah Wu, Mar 25 2024

Extensions

More terms from Vaclav Kotesovec, Mar 26 2024
Showing 1-5 of 5 results.