%I A057569
%S A057569 0,2,3,9,11,21,24,38,42,60,65,87,93,119,126,156,164,198,207,245,255,
%T A057569 297,308,354,366,416,429,483,497,555,570,632,648,714,731,801,819,
%U A057569 893,912,990,1010,1092,1113,1199,1221,1311,1334,1428,1452,1550
%N A057569 Numbers of the form n*(5n+-1)/2.
%F A057569 A005475 UNION A005476. o.g.f.: x(2x^2+x+2)/[(1-x)^3*(1+x)^2]. a(n)=A132356(n)/
               4. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 07 2008
%t A057569 #1. lst={};s=0;Do[s+=n/5;If[Floor[s]==s,AppendTo[lst,s]],{n,0,7!}];lst 
               #2. lst={};Do[AppendTo[lst,n*(5*n-1)/2];AppendTo[lst,n*(5*n+1)/2],
               {n,6!}];lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Jan 
               06 2009]
%Y A057569 Cf. A074378, A001318, A057570, A154260 [From Vladimir Orlovsky (4vladimir(AT)gmail.com), 
               Jan 06 2009]
%Y A057569 Sequence in context: A111319 A109658 A110350 this_sequence A049618 A057292 
               A098016
%Y A057569 Adjacent sequences: A057566 A057567 A057568 this_sequence A057570 A057571 
               A057572
%K A057569 nonn
%O A057569 1,2
%A A057569 N. J. A. Sloane (njas(AT)research.att.com), Oct 04 2000