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A050548
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Iterated triangular numbers with seed 7.
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9
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7, 28, 406, 82621, 3413156131, 5824817388998022646, 16964248807586870937449001943463431981, 143892868802856286225154411591351342616163027795335641150249224655238508171
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OFFSET
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0,1
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COMMENTS
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LINKS
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FORMULA
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a(n) = binomial(a(n-1)+1, 2), a(0)=7.
a(n) ~ 2 * c^(2^n), where c = 3.77579046114281148578572146955902030830005575599864345238... . - Vaclav Kotesovec, Dec 17 2014
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MATHEMATICA
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t = {7}; Do[AppendTo[t, t[[-1]]*(1 + t[[-1]])/2], {9}] (* T. D. Noe, Mar 03 2014 *)
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PROG
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(Haskell)
a050548 n = a050548_list !! n
a050548_list = iterate a000217 7
(Python)
from itertools import accumulate
def f(an, _): return an*(an+1)//2
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Dec 29 1999
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EXTENSIONS
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STATUS
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approved
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