A080382 Triangle read by rows: T(n,k) = C(n,floor(n/2))/gcd(C(n,floor(n/2)),C(n,k)), k=0..n; central binomial coefficient is divided by greatest common divisor of binomial coefficients and corresponding central binomial coefficient.

1, 1, 1, 2, 1, 2, 3, 1, 1, 3, 6, 3, 1, 3, 6, 10, 2, 1, 1, 2, 10, 20, 10, 4, 1, 4, 10, 20, 35, 5, 5, 1, 1, 5, 5, 35, 70, 35, 5, 5, 1, 5, 5, 35, 70, 126, 14, 7, 3, 1, 1, 3, 7, 14, 126, 252, 126, 28, 21, 6, 1, 6, 21, 28, 126, 252, 462, 42, 42, 14, 7, 1, 1, 7, 14, 42, 42, 462, 924, 77, 14, 21, 28

Offset

1,4

Links

Table of n, a(n) for n=1..83.

Example

Triangle begins:
   1;
   1,  1;
   2,  1,  2;
   3,  1,  1,  3;
   6,  3,  1,  3,  6;
  10,  2,  1,  1,  2, 10;
  20, 10,  4,  1,  4, 10, 20;
  35,  5,  5,  1,  1,  5,  5, 35;

Mathematica

Table[Table[Binomial[n, Floor[n/2]]/GCD[Binomial[n, j], Binomial[n, Floor[n/2]]], {j, 0, n}], {n, 1, 10}]

Crossrefs

Cf. A007318, A001405, A080381.

Sequence in context: A103823 A355246 A136642 * A349203 A106394 A325530

Adjacent sequences: A080379 A080380 A080381 * A080383 A080384 A080385

Keyword

nonn,tabl

Author

Labos Elemer, Mar 12 2003

Status

approved