Search: id:A115067
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%I A115067
%S A115067 0,4,11,21,34,50,69,91,116,144,175,209,246,286,329,375,424,476,531,589,
%T A115067 650,714,781,851,924,1000,1079,1161,1246,1334,1425,1519,1616,1716,1819,
%U A115067 1925,2034,2146,2261,2379,2500,2624,2751,2881,3014,3150,3289,3431,3576
%N A115067 (3*n^2-n-2)/2.
%H A115067 Alfred Hoehn, <a href="a000326.jpg">Illustration of initial terms of 
               A000326, A005449, A045943, A115067</a>
%F A115067 Sum (n+j,j=2..n). - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Sep 
               12 2006
%F A115067 sum(igcd(n+j,n+j),j=2..n). - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), 
               Nov 05 2006
%F A115067 If offset = 0 then a(n) = (3*n^2 + 5*n)/2 = n(3n + 5)/2. - Omar E. Pol 
               (info(AT)polprimos.com), May 21 2008
%F A115067 a(n)=3*n+a(n-1)-2 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), 
               Nov 08 2009]
%e A115067 For n=2, a(2)=3*2+0-2=4; n=3, a(3)=3*3+4-2=11; n=4, a(4)=3*4+11-2=21 
               [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 08 2009]
%p A115067 a:=n->sum(igcd(n+j,n+j),j=2..n): seq(a(n), n=1..49); - Zerinvary Lajos 
               (zerinvarylajos(AT)yahoo.com), Nov 05 2006
%p A115067 with(finance):seq(add(cashflows([2,k,n], 0 ),k=1..n),n=0..50); - Zerinvary 
               Lajos (zerinvarylajos(AT)yahoo.com), Jun 22 2008
%p A115067 a:=n->sum(k+sum(1, k=1..n), k=2..n):seq(a(n), n=1...43); [From Zerinvary 
               Lajos (zerinvarylajos(AT)yahoo.com), Aug 24 2008]
%t A115067 lst={};Do[AppendTo[lst, (3*n^2-n-2)/2], {n, 5!}];lst ...and/or... s=-1;
               lst={};Do[s+=n+1;AppendTo[lst, s], {n, 0, 6!, 3}];lst [From Vladimir 
               Orlovsky (4vladimir(AT)gmail.com), Oct 25 2008]
%Y A115067 The generalized pentagonal numbers b*n+3*n*(n-1)/2, for b = 1 through 
               12, form sequences A000326, A005449, A045943, A115067, A140090, A140091, 
               A059845, A140672, A140673, A140674, A140675, A151542.
%Y A115067 Sequence in context: A008052 A016438 A038427 this_sequence A009893 A027369 
               A008008
%Y A115067 Adjacent sequences: A115064 A115065 A115066 this_sequence A115068 A115069 
               A115070
%K A115067 nonn
%O A115067 1,2
%A A115067 Roger Bagula (rlbagulatftn(AT)yahoo.com), Mar 01 2006
%E A115067 Edited by N. J. A. Sloane (njas(AT)research.att.com), Mar 05 2006

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