A026912 a(n) = A026907(2*n-1,n-1).

13, 90, 370, 1403, 5256, 19749, 74628, 283551, 1082440, 4148594, 15953598, 61526960, 237876562, 921678867, 3577968072, 13913243127, 54184698792, 211307360862, 825059443542, 3225071709972, 12619275028602, 49423455006492, 193732625020410, 760001601263688

Offset

1,1

Links

Table of n, a(n) for n=1..24.

Formula

a(n) = binomial(2*n-1, n-1) + 3*binomial(2*n+3, n+1) - 18. - Christian Krause, May 13 2026

Crossrefs

Cf. A026907.

Sequence in context: A282858 A268746 A152867 * A161465 A162300 A161859

Adjacent sequences: A026909 A026910 A026911 * A026913 A026914 A026915

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved