A140236 a(n) = A000292(A000292(n)).

0, 1, 20, 220, 1540, 7770, 30856, 102340, 295240, 762355, 1798940, 3939936, 8104460, 15803060, 29426320, 52636760, 90889616, 152112005, 247574180, 392991060, 609896980, 927341646, 1383960600, 2030479100, 2932714200, 4175145975, 5865135276, 8137872120

Offset: 0

Author

Artur Jasinski, May 14 2008

Keywords

• nonn
• easy

Links

• N. J. A. Sloane, Table of n, a(n) for n = 0..10000
• Index entries for linear recurrences with constant coefficients, signature (10,-45,120,-210,252,-210,120,-45,10,-1).

Crossrefs

Row n=3 of A331436.

Cf. A000292.

Programs

Maple

a:= (n-> binomial(n+2,3))@@2:
seq(a(n), n=0..29);  # Alois P. Heinz, Mar 11 2024

Mathematica

Table[(n (1 + n) (2 + n) (3 + n) (2 + n^2) (12 + n (1 + n) (2 + n)))/1296,{n,0,20}]

PARI

b(n)=n*(n+1)*(n+2)/6;
a(n)=b(b(n));
vector(25,n,a(n-1)) \\ Joerg Arndt, Mar 11 2024

Formula

a(n) = (n*(1 + n)*(2 + n)*(3 + n)*(2 + n^2)*(12 + n*(1 + n)*(2 + n)))/1296.

G.f.: x*(1+10*x+65*x^2+120*x^3+80*x^4+4*x^5)/(1-x)^10. - Colin Barker, Apr 30 2012.