A099187 Let D(n) = n*(9*n^2-9*n+2)/2 then a(k+1) = D(a(k)) and a(0) = 1.

1, 20, 34220, 180318314012420, 26383476911029432816173777932463879690054620

Offset: 1

Author

Jonathan Vos Post, Nov 15 2004

Keywords

• easy
• nonn

Links

• Michel Marcus, Table of n, a(n) for n = 0..6
• Hyun Kwang Kim, On Regular Polytope Numbers, Proc. Amer. Math. Soc., 131 (2003), 65-75.

Crossrefs

Cf. A007501, A006566.

Programs

Mathematica

Dod[n_]:= n*(9*n^2-9*n+2)/2;
a[n_]:= If[n==0, Dod[1], If[n==1, Dod[2], Dod[a[n-1]]]];
Table[a[n], {n, 0, 4}] (* G. C. Greubel, Mar 22 2019 *)

PARI

dod(n) = n*(9*n^2-9*n+2)/2;
a(n) = if (n==0, 1, if (n==1, dod(2), dod(a(n-1)))); \\ Michel Marcus, Dec 14 2015

Formula

Let D(n) = n*(9*n^2-9*n+2)/2 then a(k+1) = D(a(k)) and a(0) = 1.