A145874 Number of permutations of the numbers 1, 2, ..., n such that for all 1 <= k <= n the average of the first k numbers is at least the average of all n numbers.

1, 1, 3, 7, 35, 139, 1001, 5701, 53109, 402985, 4605271

Offset

1,3

Comments

Same as A147681.

Links

Table of n, a(n) for n=1..11.

Example

For n = 3, the 3 permutations are (2,3,1), (3,1,2) and (3,2,1).

Prog

(PARI) a(n) = {nbok = 0; avg = (n+1)/2; for (j = 1, n!, perm = numtoperm(n, j); ok = 1; for (k = 1, n, if (sum(j=1, k, perm[j])/k < avg, ok = 0; break; ); ); if (ok, nbok++); ); nbok; } \\ Michel Marcus, Aug 12 2013

Crossrefs

Sequence in context: A328420 A336012 A212417 * A147681 A055487 A121130

Adjacent sequences: A145871 A145872 A145873 * A145875 A145876 A145877

Keyword

nonn,more

Author

N. Sato, Oct 22 2008

Extensions

a(7)-a(11) from Michel Marcus, Aug 12 2013

Status

approved