%I A045945
%S A045945 0,12,42,90,156,240,342,462,600,756,930,1122,1332,1560,1806,2070,2352,
%T A045945 2652,2970,3306,3660,4032,4422,4830,5256,5700,6162,6642,7140,7656,8190,
%U A045945 8742,9312,9900,10506,11130,11772,12432,13110,13806,14520,15252,16002
%N A045945 Hexagonal matchstick numbers: 3n(3n+1).
%F A045945 a(n)=18*n+a(n-1)-24 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), 
               Nov 13 2009]
%e A045945 For n=2, a(2)=18*2+0-24=12; n=3, a(3)=18*3+12-24=42; n=4, a(4)=18*4+42-24=90 
               [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 13 2009]
%p A045945 a:=n->sum(n+1, j=1..n): seq(a(n*3), n=0..42); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), 
               May 03 2007
%Y A045945 Cf. A033580, A045946.
%Y A045945 Sequence in context: A022672 A109275 A085798 this_sequence A005901 A090554 
               A009948
%Y A045945 Adjacent sequences: A045942 A045943 A045944 this_sequence A045946 A045947 
               A045948
%K A045945 nonn,new
%O A045945 0,2
%A A045945 R. K. Guy