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.

A240673 Triangle read by rows: T(n, k) = v(n, k)*((1/v(n, k)) mod prime(k)), where v(n, k) = (Product_{j=1..n} prime(j))/prime(k), n >= 1, 1 <= k <= n.

Original entry on oeis.org

1, 3, 4, 15, 10, 6, 105, 70, 126, 120, 1155, 1540, 1386, 330, 210, 15015, 20020, 6006, 25740, 16380, 6930, 255255, 170170, 306306, 145860, 46410, 157080, 450450, 4849845, 3233230, 3879876, 8314020, 6172530, 3730650, 9129120, 9189180
Offset: 1

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Author

Michel Marcus, Apr 10 2014

Keywords

Comments

These coefficients have the following property: for any number j in 0..primorial(n)-1, j = Sum_{i=1..n} T(n,k)*(j mod prime(i)) mod primorial(n). For example, with the first 3 primes (2, 3, and 5) and j=47, j is [47 mod 2, 47 mod 3, 47 mod 5] = [1, 2, 2], and 15*1 + 10*2 + 6*2 = 15 + 20 + 12 = 47.

Examples

			Triangle starts:
     1;
     3,    4;
    15,   10,    6;
   105,   70,  126,  120;
  1155, 1540, 1386,  330,  210;
		

Crossrefs

Cf. A000040 (primes), A002110 (primorials), A070826 (first column), A079276.

Programs

  • Maple
    T := proc(n, k)
    v := mul(ithprime(j), j=1..n)/ithprime(k);
    v * ((1/v) mod ithprime(k)) end:
    seq(print(seq(T(n,k), k=1..n)), n=1..7); # Peter Luschny, Apr 12 2014
  • Mathematica
    lift[Rational[1, n_], p_] := Module[{m}, m /. Solve[n*m == 1, m, Modulus -> p][[1]]]; lift[1, 2] = 1;
    v[n_, k_] := Product[Prime[j], {j, 1, n}]/Prime[k];
    T[n_, k_] := v[n, k]*lift[1/v[n, k], Prime[k]];
    Table[T[n, k], {n, 1, 8}, {k, 1, n}] // Flatten (* Jean-François Alcover, Nov 30 2017 *)
  • PARI
    T(n, k) = {my(val = prod(j=1, n, prime(j))/prime(k)); val * lift(1/Mod(val, prime(k)));}

Formula

T(n, k) = v(n, k) * ((1/v(n, k)) mod prime(k)), where v(n, k) = Product_{j=1..n} prime(j)/prime(k).
T(n, n) = A002110(n-1) * A079276(n). - Peter Luschny, Apr 12 2014