|
%I #20 Sep 29 2023 18:58:55
%S 5,15,120,7260,26357430,347357071281165,60328467484514345085777519195,
%T 1819761994515052295911016533077539330911500847167185483610
%N Iterated triangular numbers with seed 5.
%H Reinhard Zumkeller, <a href="/A050542/b050542.txt">Table of n, a(n) for n = 0..11</a>
%F a(n) = binomial(a(n-1)+1, 2), a(0)=5.
%F a(n) ~ 2 * c^(2^n), where c = 2.786070277619247476352890606543375642991890742669788965024... . - _Vaclav Kotesovec_, Dec 17 2014
%t 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 *)
%t NestList[Binomial[#+1,2]&,5,9] (* _Harvey P. Dale_, Sep 24 2011 *)
%o (Haskell)
%o a050542 n = a050542_list !! n
%o a050542_list = iterate a000217 5 -- _Reinhard Zumkeller_, Apr 10 2014
%o (PARI) a(n)=if(n, binomial(a(n-1)+1, 2), 5) \\ _Charles R Greathouse IV_, Feb 08 2017
%Y Cf. A000217, A007501, A013589, A050536, A050548, A050909.
%K easy,nice,nonn
%O 0,1
%A Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Dec 29 1999
|
