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A141499
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a(0)=0; a(1)=1; a(n) = triangular number at index 5*2^(n-2)-1.
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0
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0, 1, 10, 45, 190, 780, 3160, 12720, 51040, 204480, 818560, 3275520, 13104640, 52423680, 209704960, 838840320, 3355402240, 13421690880, 53686927360, 214748037120, 858992803840
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| The sequence a(n)=b(n)*(b(n)-1)/2 gives an SO(2),SO(5),SO(10),SO(20), ...
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FORMULA
| a(0)=0. a(n)=A000217(A052549(n-1)), n>0. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 29 2008
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MATHEMATICA
| Clear[a] a[0] = 1; a[1] = 2; a[2] = 5; a[n_] := a[n] = a[1]*a[n - 1]; Table[a[n]*(a[n] - 1)/2, {n, 0, 20}]
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CROSSREFS
| Cf. A084215.
Sequence in context: A005714 A175705 A143671 * A061772 A032165 A124174
Adjacent sequences: A141496 A141497 A141498 * A141500 A141501 A141502
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KEYWORD
| nonn
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AUTHOR
| Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Aug 10 2008
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Aug 16 2008
Corrected the definition, which was describing an auxiliary sequence. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 29 2008
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