document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1083509>Question 1083509</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 3, -6, 12, 4, 20, ?     can not figure this out....<BR>\n" );
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document.write( "3,-6,12,4,20,n\r<BR>\n" );
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document.write( "I think  n = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+highlight%2813%29+ ALIGN=MIDDLE  ALT=\"+highlight%2813%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > (?)<BR>\n" );
document.write( "—\r<BR>\n" );
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document.write( "Based on the partial sequence, the differences are<BR>\n" );
document.write( "   -9, +18, -8, +16\r<BR>\n" );
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document.write( "So I'd guess the next difference would be -7,  and 20-7 = 13. </SPAN>\n" );
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