A051290 Triangular array T read by rows: T(n,k)=P(2n+3,n,2k+3), where P(n,k,c)=number of vectors (x(1),x(2,),...,x(n)) of k 1's and n-k 0's such that x(i)=x(n+1-i) for exactly c values of i.

1, 4, 1, 12, 6, 3, 32, 24, 24, 4, 80, 80, 120, 40, 10, 192, 240, 480, 240, 120, 15, 448, 672, 1680, 1120, 840, 210, 35, 1024, 1792, 5376, 4480, 4480, 1680, 560, 56, 2304, 4608, 16128, 16128, 20160, 10080, 5040, 1008, 126

Offset

0,2

Comments

P(n,k,n) counts palindromes.

Links

Table of n, a(n) for n=0..44.

Example

Triangle begins:
   1;
   4,  1;
  12,  6,   3;
  32, 24,  24, 4,
  80, 80, 120, 40, 10;
  ...

Crossrefs

Cf. A051287, A051288, A051289.

Sequence in context: A272099 A329033 A217234 * A227338 A125105 A144878

Adjacent sequences: A051287 A051288 A051289 * A051291 A051292 A051293

Keyword

nonn,tabl

Author

Clark Kimberling

Status

approved