document.write( "Question 586731: I need an explicit formula for the sequence : {2, 6, 12, 20} I have noticed that the pattern is +4, +6, +8 and so on, but I can't figure out how to write the formula. \n" ); document.write( "

Algebra.Com's Answer #373858 by ad_alta(240) $\"\"$ $\"About$

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Use A(n)=n(n+1) [since 1(1+1)=2, 2(2+1)=6)...4(4+1)=20] \n" ); document.write( "

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