A293047 Number of odd permutations on {1,2,...,n} with exactly 2 weak excedances.

0, 0, 0, 3, 4, 15, 26, 63, 120, 255, 502, 1023, 2036, 4095, 8178, 16383, 32752, 65535, 131054, 262143, 524268, 1048575, 2097130, 4194303, 8388584, 16777215, 33554406, 67108863, 134217700, 268435455, 536870882, 1073741823, 2147483616, 4294967295, 8589934558

Offset

0,4

Links

Table of n, a(n) for n=0..34.

Dmitry Efimov, Determinants of generalized binary band matrices, arXiv:1702.05655 [math.RA], 2017.

Formula

a(n) = (A000295(n) + (-1)^n * (n-1))/2, n > 0.

a(n) = 2^(n-1) - 1 for odd n.

Crossrefs

Cf. A000295, A293046.

Sequence in context: A081405 A167367 A024858 * A135100 A205485 A344261

Adjacent sequences: A293044 A293045 A293046 * A293048 A293049 A293050

Keyword

nonn

Author

Eric M. Schmidt, Oct 09 2017

Status

approved