A026970 a(n) = Sum_{k=0..n} (k+1) * A026637(n,k).

1, 3, 8, 25, 60, 147, 336, 765, 1700, 3751, 8184, 17745, 38220, 81915, 174752, 371365, 786420, 1660239, 3495240, 7340025, 15379100, 32156323, 67108848, 139810125, 290805060, 603979767, 1252698776, 2594876065, 5368709100

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Formula

Conjectures from Colin Barker, Feb 18 2016: (Start)

a(n) = -((-1)^n-2^(n+2)+3)*(n+2)/6 for n>0.

a(n) = 4*a(n-1)-2*a(n-2)-8*a(n-3)+7*a(n-4)+4*a(n-5)-4*a(n-6) for n>6.

G.f.: (1-x-2*x^2+7*x^3-7*x^4-4*x^5+4*x^6) / ((1-x)^2*(1+x)^2*(1-2*x)^2).

(End)