A172010 a(n) = 2*A142458(2*n, n)/(n+1).

1, 26, 2741, 683870, 315704418, 234725594388, 257237392999893, 390832857108454838, 787178784737043042806, 2031210797603911366282796, 6536955866068372922068141666, 25676217636579568989377656129516, 120915166829869713032692550819662756, 672580820552232143302651758669053327784

Offset

1,2

Links

G. C. Greubel, Table of n, a(n) for n = 1..190

Formula

a(n) = 2*A142458(2*n, n)/(n+1).

Mathematica

T[n_, k_, m_]:= T[n, k, m]= If[k==1 || k==n, 1, (m*n-m*k+1)*T[n-1, k-1, m] + (m*k-m+ 1)*T[n-1, k, m]];
a[n_]:= 2*T[2*n, n, 3]/(n+1);
Table[a[n], {n, 30}] (* modified by G. C. Greubel, Mar 14 2022 *)

Prog

(Sage)
@CachedFunction
def T(n, k, m): # A142458
    if (k==1 or k==n): return 1
    else: return (m*(n-k)+1)*T(n-1, k-1, m) + (m*k-m+1)*T(n-1, k, m)
[2*T(2*n, n, 3)/(n+1) for n in (1..30)] # G. C. Greubel, Mar 14 2022

Crossrefs

Cf. A142458, A177042, A177043.

Sequence in context: A232159 A263946 A358164 * A283571 A377637 A283041

Adjacent sequences: A172007 A172008 A172009 * A172011 A172012 A172013

Keyword

nonn

Author

Roger L. Bagula, Nov 19 2010

Extensions

Name corrected and more terms added by G. C. Greubel, Mar 14 2022

Status

approved