A168234 - OEIS

%I #3 Mar 30 2012 18:52:04

%S 3,3,13,13,13,13,13,13,13,13,39,39,39,39,39,39,39,39,39,39,39,39,39,

%T 39,39,39,39,39,89,89,89,89,89,89,89,89,89,89,89,89,89,89,89,89,89,89,

%U 89,89,89,89,89,89,89,89,89,89,89,89,89,89,171,171,171,171,171,171,171

%N A138100(n) + A168142(n).

%C A138100 counts upwards in blocks of 2*k^2 numbers, restarting from 1,5,21,57,.. = A166464(k-1) = (2*k+1)*(2*k^2-4*k+3)/3, k>=1.

%C A168142 counts downwards in blocks of 2*k^2 numbers, restarting from 2*k^2, k>=1.

%C In consequence, the sequence here contains 2*k^2 copies of the number 1+2*k*(1+2*k^2)/3 = 1+A035597(k), k>=1,

%C where the sequence A035597 is a bisection of A168380.

%Y Cf. A134984, A138725, A168208.

%K nonn,less

%O 1,1

%A _Paul Curtz_, Nov 21 2009

%E Edited by _R. J. Mathar_, Feb 15 2010