OFFSET
0,1
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 0..11
FORMULA
a(n) = binomial(a(n-1)+1, 2), a(0)=5.
a(n) ~ 2 * c^(2^n), where c = 2.786070277619247476352890606543375642991890742669788965024... . - Vaclav Kotesovec, Dec 17 2014
MATHEMATICA
a=5; lst={a}; Do[b=(a+1)*a/2; AppendTo[lst, b]; a=b, {n, 1, 9}]; lst ( Vladimir Joseph Stephan Orlovsky, Mar 16 2010 *)
NestList[Binomial[#+1, 2]&, 5, 9] (* Harvey P. Dale, Sep 24 2011 *)
PROG
(Haskell)
a050542 n = a050542_list !! n
a050542_list = iterate a000217 5 -- Reinhard Zumkeller, Apr 10 2014
(PARI) a(n)=if(n, binomial(a(n-1)+1, 2), 5) \\ Charles R Greathouse IV, Feb 08 2017
CROSSREFS
KEYWORD
easy,nice,nonn
AUTHOR
Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Dec 29 1999
STATUS
approved