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A141499 a(0)=0; a(1)=1; a(n) = triangular number at index 5*2^(n-2)-1. +0
1
0, 1, 10, 45, 190, 780, 3160, 12720, 51040, 204480, 818560, 3275520, 13104640, 52423680, 209704960, 838840320, 3355402240, 13421690880, 53686927360, 214748037120, 858992803840 (list; graph; listen)
OFFSET

0,3

COMMENT

The sequence a(n)=b(n)*(b(n)-1)/2 gives an SO(2),SO(5),SO(10),SO(20), ...

FORMULA

a(0)=0. a(n)=A000217(A052549(n-1)), n>0. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 29 2008

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}]

CROSSREFS

Cf. A084215.

Sequence in context: A027800 A005714 A143671 this_sequence A061772 A032165 A124174

Adjacent sequences: A141496 A141497 A141498 this_sequence A141500 A141501 A141502

KEYWORD

nonn

AUTHOR

Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Aug 10 2008

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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Last modified December 20 16:54 EST 2009. Contains 171081 sequences.


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