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A050536 Iterated triangular numbers. 10
8, 36, 666, 222111, 24666759216, 304224505122393846936, 46276274758482720006792605816457695217516, 1070746802761292462947634762387664148872006333922794021004562705432032738124213886 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..10

FORMULA

a(n) = binomial(a(n-1)+1, 2), a(0)=8.

a(n) ~ 2 * c^(2^n), where c = 4.2726038862497240421168669075178596377687659229240586312... . - Vaclav Kotesovec, Dec 17 2014

MATHEMATICA

NestList[Binomial[#+1, 2]&, 8, 7] (* Harvey P. Dale, Jan 22 2016 *)

PROG

(Haskell)

a050536 n = a050536_list !! n

a050536_list = iterate a000217 8  -- Reinhard Zumkeller, Apr 10 2014

(PARI) a(n)=if(n==0, 8, (a(n-1))*(a(n-1)+1)/2) \\ Edward Jiang, Sep 07 2014

CROSSREFS

Cf. A000217.

Cf. A007501, A013589, A050542, A050548, A050909.

Sequence in context: A268157 A203020 A276175 * A261846 A110215 A281465

Adjacent sequences:  A050533 A050534 A050535 * A050537 A050538 A050539

KEYWORD

easy,nice,nonn

AUTHOR

Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Dec 29 1999

EXTENSIONS

One more term (a(7)) from Harvey P. Dale, Jan 22 2016

STATUS

approved

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Last modified February 18 17:08 EST 2018. Contains 299325 sequences. (Running on oeis4.)