%I A005120 M3770
%S A005120 0,1,1,1,1,1,5,8,7,1,19,43,55,27,64,211,343,307,85,911,1919,2344,989,
%T A005120 3151,9625,15049,12609,5671,42496,85609,100225,33977,154007,437009,
%U A005120 657901,513512,335665,1974097,3808891,4265379
%V A005120 0,1,-1,1,-1,-1,5,-8,7,1,-19,43,-55,27,64,-211,343,-307,-85,911,-1919,
               2344,-989,-3151,
%W A005120 9625,-15049,12609,5671,-42496,85609,-100225,33977,154007,-437009,657901,
               -513512,
%X A005120 -335665,1974097,-3808891,4265379
%N A005120 a(n+6) = -3a(n+5)-5a(n+4)-5a(n+3)-5a(n+2)-3a(n+1)-a(n).
%C A005120 This is a divisibility sequence. If d divides n then a(d) divides a(n).
%D A005120 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005120 M. Duboue, Une suite recurrente remarquable, Europ. J. Combin., 4 (1983), 
               205-214.
%D A005120 H. C. Williams, Edouard Lucas and Primality Testing, Wiley, 1998, p. 
               455. Math. Rev. 2000b:11139
%F A005120 G.f.: x(1+2x+3x^2+2x^3+x^4)/(1+3x+5x^2+5x^3+5x^4+3x^5+x^6).
%o A005120 (PARI) a(n)=polcoeff(x*(1+2*(x+x^3)+3*x^2+x^4)/(1+3*(x+x^5)+5*(x^2+x^3+x^4)+x^6)+x*O(x^n),
               n)
%Y A005120 Cf. A001608.
%Y A005120 Sequence in context: A160043 A145432 A070371 this_sequence A133731 A021067 
               A047914
%Y A005120 Adjacent sequences: A005117 A005118 A005119 this_sequence A005121 A005122 
               A005123
%K A005120 sign,easy
%O A005120 0,7
%A A005120 N. J. A. Sloane (njas(AT)research.att.com).
%E A005120 Edited by Michael Somos, Aug 02, 2002