%I A067725
%S A067725 0,9,24,45,72,105,144,189,240,297,360,429,504,585,672,765,864,969,1080,
%T A067725 1197,1320,1449,1584,1725,1872,2025,2184,2349,2520,2697,2880,3069,3264,
%U A067725 3465,3672,3885,4104,4329,4560,4797,5040,5289,5544,5805,6072,6345,6624
%N A067725 a(n) = 3n^2 + 6n.
%C A067725 Numbers such that 3*(3 + n) is a perfect square. - Alex Healy (blink2826(AT)aol.com), 
               Tj Tullo, Avery Pickford, Sep 20 2004
%C A067725 a(n)=3*A005563 - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 06 
               2007
%F A067725 a(n)=6*n+a(n-1)-3 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), 
               Nov 08 2009]
%e A067725 For n=2, a(2)=6*2+0-3=9; n=3, a(3)=6*3+9-3=24; n=4, a(4)=6*4+24-3=45 
               [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 08 2009]
%p A067725 a:=n->sum(sum(3, j=2..n), k=0..n): seq(a(n), n=1..40); - Zerinvary Lajos 
               (zerinvarylajos(AT)yahoo.com), May 30 2007
%p A067725 [seq((n+(n+1)+(n+2))*(n+3),n=0..49)]; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), 
               Jun 24 2006
%p A067725 a:=n->sum(sum(3, j=2..n), k=0..n): seq(a(n), n=2..47); - Zerinvary Lajos 
               (zerinvarylajos(AT)yahoo.com), May 30 2007
%t A067725 Select[ Range[10000], IntegerQ[ Sqrt[ 3(3 + # )]] & ]
%Y A067725 Cf. A005563.
%Y A067725 Cf. 8: A067728, 7: A067727, 6: A067726, 5: A067724.
%Y A067725 Sequence in context: A161449 A063066 A097658 this_sequence A001106 A023551 
               A022787
%Y A067725 Adjacent sequences: A067722 A067723 A067724 this_sequence A067726 A067727 
               A067728
%K A067725 nonn
%O A067725 0,2
%A A067725 Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 05 2002
%E A067725 Edited by N. J. A. Sloane (njas(AT)research.att.com), Sep 14 2008 at 
               the suggestion of R. J. Mathar