%I
%S 1,1,2,3,4,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,1,
%T 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,1,2,
%U 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28
%N Write numbers 1, then 1 up to 2^2, then 1 up to 3^2, then 1 up to 4^2 and so on.
%C This is a fractal sequence: if the first instance of each number is deleted, the original sequence is recovered.  _Franklin T. AdamsWatters_, Dec 14 2013
%C Subsequences start at indices A000330 + 1.  _Ralf Stephan_, Dec 17 2013
%C When sequence fills a triangular array by rows, the main diagonal is A064865:
%C This triangle begins:
%C ....1
%C ...1.2
%C ..3.4.1
%C .2.3.4.5
%C 6.7.8.9.1
%C From _Antti Karttunen_, Feb 17 2014: (Start)
%C A more natural way of organizing this sequence is as an irregular table consisting of successively larger square matrices:
%C 1;
%C 1, 2;
%C 3, 4;
%C 1, 2, 3;
%C 4, 5, 6;
%C 7, 8, 9;
%C 1, 2, 3, 4;
%C 5, 6, 7, 8;
%C 9,10,11,12;
%C 13,14,15,16;
%C etc.
%C (End)
%F a(n) = A237451(n) + (A237452(n)*A074279(n)) + 1.  _M. F. Hasler_, Feb 17 2014
%F For 1 <= n <= 650, a(n) = n  t(t1)(2t1)/6, where t = floor((3*n)^(1/3)+1/2).  _Mikael Aaltonen_, Jan 17 2015
%o (PARI) A064866_vec(N=9)=concat(vector(N, i, vector(i^2, j, j))) \\ NB: This creates a vector; use A064866_vec()[n] to get the nth term.  _M. F. Hasler_, Feb 17 2014
%Y Cf. A002260, A002262, A002024.
%Y Cf. A074279, A121997, A238013, A237451, A237452.
%K easy,nonn,tabl
%O 1,3
%A Floor van Lamoen (fvlamoen(AT)hotmail.com), Oct 08 2001
%E Edited by _Ralf Stephan_, Dec 17 2013
