document.write( "Question 166155: How to derive Nth term of the following series?\r
\n" ); document.write( "\n" ); document.write( "1,3,6,10,15,21.........upto n terms 25!!!!!!!!!!!!!!!!!!!!!!!!! \n" ); document.write( "
Algebra.Com's Answer #122459 by Fombitz(32388)\"\" \"About 
You can put this solution on YOUR website!
Look at the difference between terms,
\n" ); document.write( "1,3=2
\n" ); document.write( "3,6=3
\n" ); document.write( "6,10=4
\n" ); document.write( "10,15=5
\n" ); document.write( "15,21=6
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\n" ); document.write( "First term=1
\n" ); document.write( "Second term=First term +2=1+2
\n" ); document.write( "Third term=Second term+3=1+2+3
\n" ); document.write( "Fourth term=Third term+4=1+2+3+4
\n" ); document.write( "Starting to see a pattern here...
\n" ); document.write( "Nth term=(N-1)term+N=1+2+3+...+(N-1)+N
\n" ); document.write( "Look like the terms follow,
\n" ); document.write( "\"T%5BN%5D=sum%28+i%2C+i=1%2C+N+%29\"
\n" ); document.write( "\"T%5B25%5D=sum%28+i%2C+i=1%2C+25+%29=325\" \n" ); document.write( "
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