A077002 a(1) = 1, a(n+1) is the largest triangular number <= n*a(n).

1, 1, 1, 3, 10, 45, 253, 1770, 14028, 125751, 1256905, 13825911, 165902220, 2156701326, 30193705191, 452904989670, 7246477931241, 123190111062756, 2217421939553376, 42131016700673761, 842620333202031306

Offset

1,4

Links

Harvey P. Dale, Table of n, a(n) for n = 1..451

Maple

a[1] := 1:for n from 2 to 100 do a[n] := floor(evalf(-1/2+1/2*sqrt(1+8*(n-1)*a[n-1])+1/10^50, 300)):a[n] := a[n]*(a[n]+1)/2:od:seq(a[l], l=1..100);

Mathematica

nxt[{n_, a_}]:=Module[{c=Floor[(Sqrt[1+8n*a]-1)/2]}, {n+1, (c(c+1))/2}]; NestList[nxt, {1, 1}, 20][[All, 2]] (* Harvey P. Dale, Jun 04 2021 *)

Crossrefs

Cf. A077003.

Sequence in context: A099237 A006220 A020026 * A268224 A003704 A292181

Adjacent sequences: A076999 A077000 A077001 * A077003 A077004 A077005

Keyword

nonn

Author

Amarnath Murthy, Oct 26 2002

Extensions

More terms from Sascha Kurz, Jan 26 2003

Status

approved