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 1-3 of 3 results.

A199333 Triangle read by rows: T(n,0) = T(n,n) = 1, 0 < k < n: T(n,k) = smallest prime not less than T(n-1,k) + T(n-1,k-1).

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 3, 1, 1, 5, 7, 5, 1, 1, 7, 13, 13, 7, 1, 1, 11, 23, 29, 23, 11, 1, 1, 13, 37, 53, 53, 37, 13, 1, 1, 17, 53, 97, 107, 97, 53, 17, 1, 1, 19, 71, 151, 211, 211, 151, 71, 19, 1, 1, 23, 97, 223, 367, 431, 367, 223, 97, 23, 1, 1, 29, 127
Offset: 0

Views

Author

Reinhard Zumkeller, Nov 09 2011

Keywords

Comments

T(n,k) = T(n,n-k);
T(n,0) = 1, cf. A000012;
T(n,1) = A008578(n), n > 0;
A199424(n) = first row in triangle A199302 containing n-th prime;
A199425(n) = number of distinct primes in rows 0 through n;
large terms in the b-file are probable primes only, row number > 50.

Examples

			0:                 1
1:               1   1
2:             1   2   1
3:           1   3   3   1
4:         1   5   7   5   1
5:       1   7  13  13   7   1
6:     1  11  23  29  23  11   1
7:   1  13  37  53  53  37  13   1
8: 1  17  53  97 107  97  53  17   1
primes in 8th row:
T(7,0) + T(7,1) = 1+13 = 14 --> T(8,1) = T(8,7) = 19;
T(7,1) + T(7,2) = 13+37 = 50 --> T(8,2) = T(8,6) = 53, already in row 7;
T(7,2) + T(7,3) = 37+53 = 90 --> T(8,3) = T(8,5) = 97;
T(7,3) + T(7,4) = 53+53 = 106 --> T(8,4) = 107.
		

Crossrefs

Cf. A159477; A199581 & A199582 (central terms), A199694 (row sums), A199695 & A199696 (row products); A007318.

Programs

  • Haskell
    a199333 n k = a199333_tabl !! n !! k
    a199333_row n = a199333_tabl !! n
    a199333_list = concat a199333_tabl
    a199333_tabl = iterate
       (\row -> map a159477 $ zipWith (+) ([0] ++ row) (row ++ [0])) [1]
  • Mathematica
    T[n_, k_] := T[n, k] = Switch[k, 0|n, 1, _, With[{m = T[n-1, k] + T[n-1, k-1]}, If[PrimeQ[m], m, NextPrime[m]]]];
    Table[T[n, k], {n, 0, 13}, {k, 0, n}] // Flatten (* Jean-François Alcover, Sep 19 2021 *)

Formula

T(n,k) = A007918(T(n-1,k) + T(n-1,k-1)), 0 < k < n, T(n,0) = T(n,n) = 1.

A199582 Central terms of the triangle in A199333: a(n) = A199333(n,[n/2]).

Original entry on oeis.org

1, 1, 2, 3, 7, 13, 29, 53, 107, 211, 431, 809, 1619, 3037, 6079, 11467, 22937, 43541, 87083, 166183, 332393, 636761, 1273541, 2448049, 4896103, 9438851, 18877711, 36484271, 72968563, 141332173, 282664351, 548544487, 1097088989, 2132671027, 4265342057
Offset: 0

Views

Author

Reinhard Zumkeller, Nov 09 2011

Keywords

Comments

a(n) = max(A199333(n,k): 0<=k<=n/2) = A006530(A199695(n)) = A006530(A199696(n));
a(2*n) = A007918(a(2*n-1)) for n > 0.

Crossrefs

Programs

  • Haskell
    a199582 n = a199333_row n !! (n `div` 2)

A199695 Row products of the triangle in A199333.

Original entry on oeis.org

1, 1, 2, 9, 175, 8281, 1856261, 649893049, 817291210163, 1847322434679121, 14368726069959027071, 342031303262647675287601, 13964481217238950868653586531, 1889891784470148590323094656731121, 586215019967842464352819482405063771511
Offset: 0

Views

Author

Reinhard Zumkeller, Nov 09 2011

Keywords

Comments

a(n) = Product_{k=0..n} A199333(n,k);
A199696(n) = A007947(a(n));
A020639(a(n)) = A008578(n); A006530(a(n)) = A199582(n).

Crossrefs

Programs

  • Haskell
    a199695 = product . a199333_row
Showing 1-3 of 3 results.