Search: id:A002348
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%I A002348 M0549 N0198
%S A002348 1,2,3,4,6,8,9,12,15,16,21,24,24,32,36,36,45,48,48,60,66,64,75,84,81,
%T A002348 96,105,96,120,128,120,144,144,144,171,180,168,192,210,192,231,240,
%U A002348 216,264,276,256,294,300,288,336,351,324,360,384,360,420,435,384,465
%N A002348 Degree of rational Poncelet porism of n-gon.
%D A002348 Kerawala, S. M.; Poncelet Porism in Two Circles. Bull. Calcutta Math. 
               Soc. 39, 85-105, 1947.
%D A002348 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002348 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A002348 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               PonceletsPorism.html">Link to a section of The World of Mathematics.</
               a>
%t A002348 Poncelet[ n_Integer /; n >= 3 ] := Module[ {p, a, i}, {p, a}=Transpose[ 
               FactorInteger[ n ] ];
%t A002348 If[ p[ [ 1 ] ]==2, 4^a[ [ 1 ] ]Product[ p[ [ i ] ]^(2(a[ [ i ] ]-1))(p[ 
               [ i ] ]^2-1), {i, 2, Length[ p ]} ]/8, (* Else *) Product[ p[ [ i 
               ] ]^(2(a[ [ i ] ]-1))(p[ [ i ] ]^2-1), {i, Length[ p ]} ]/8 ] ]
%o A002348 (PARI) a(n)= local(p,e); if(n<3,0, p=factor(n)~; e=p[2,]; p=p[1,]; if(p[1]==2,
               4^e[1],1)* prod(i=1+(p[1]==2),length(p),p[i]^(2*(e[i]-1))* (p[i]^2-1))/
               8) - Michael Somos, Dec 09 1999
%Y A002348 Sequence in context: A033501 A097273 A006446 this_sequence A019469 A081491 
               A161826
%Y A002348 Adjacent sequences: A002345 A002346 A002347 this_sequence A002349 A002350 
               A002351
%K A002348 nonn,nice
%O A002348 3,2
%A A002348 N. J. A. Sloane (njas(AT)research.att.com).
%E A002348 Extended with Mathematica program by Eric Weisstein (eric(AT)weisstein.com)

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