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A061600 a(n) = n^3 - n + 1. 6

%I

%S 1,1,7,25,61,121,211,337,505,721,991,1321,1717,2185,2731,3361,4081,

%T 4897,5815,6841,7981,9241,10627,12145,13801,15601,17551,19657,21925,

%U 24361,26971,29761,32737,35905,39271,42841,46621,50617,54835,59281,63961

%N a(n) = n^3 - n + 1.

%C Smallest of n consecutive odd numbers whose sum is n^4. (n^k can be expressed as the sum of n consecutive odd numbers the smallest of which is given by n^(k-1)-n+1.)

%D T. A. Gulliver, Sequences from Cubes of Integers, Int. Math. Journal, 4 (2003), 439-445.

%H Harry J. Smith, <a href="/A061600/b061600.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).

%F G.f.: (1-3*x+9*x^2-x^3)/(1 - x)^4. a(-n) = -A126420(n). - _Bruno Berselli_, Aug 29 2011

%F a(n) = 1 + Sum_{k=1..n} 3*(k-1)*k. - _Luce ETIENNE_ and _Michel Marcus_, Nov 01 2014

%e a(5) = 121 = 5^3 - 5 + 1. We have 121 + 123 + 125 + 127 + 129 = 625 = 5^4.

%t Table[n^3 - n + 1, {n, 0, 40}] (* _Vladimir Joseph Stephan Orlovsky_, Feb 20 2012 *)

%o (PARI) { for (n=0, 1000, write("b061600.txt", n, " ", n^3 - n + 1) ) } \\ _Harry J. Smith_, Jul 25 2009

%o (MAGMA) [n^3 - n + 1: n in [0..40]]; // _Vincenzo Librandi_, Aug 29 2011

%K nonn,easy

%O 0,3

%A _Amarnath Murthy_, May 19 2001

%E Offset changed from 1 to 0 by _Harry J. Smith_, Jul 25 2009

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Last modified January 29 04:57 EST 2020. Contains 331335 sequences. (Running on oeis4.)