Pretty hard sequence 2.

Algebra Level pending

What is the next term in the sequence

1 1 , 7 7 , 21 21 , 46 46 , 85 85 , 141 141 .....?


The answer is 217.

Shivamani Patil by shivamani patil , 21, India

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2 solutions

Kenny Lau
Jul 10, 2014

Sequence: 1 , 7 , 21 , 46 , 85 , 141 First difference: 6 , 14 , 25 , 39 , 56 Second difference: 8 , 11 , 14 , 17 Third difference: 3 , 3 , 3 \begin{array}{lc} \mbox{Sequence:}&1&,&7&,&21&,&46&,&85&,&141\\ \mbox{First difference:}&&6&,&14&,&25&,&39&,&56\\ \mbox{Second difference:}&&&8&,&11&,&14&,&17\\ \mbox{Third difference:}&&&&3&,&3&,&3 \end{array}

Sequence: 1 , 7 , 21 , 46 , 85 , 141 , 217 First difference: 6 , 14 , 25 , 39 , 56 , 76 Second difference: 8 , 11 , 14 , 17 , 20 Third difference: 3 , 3 , 3 , 3 \begin{array}{lc} \mbox{Sequence:}&1&,&7&,&21&,&46&,&85&,&141&,&\color{#20A900}{217}\\ \mbox{First difference:}&&6&,&14&,&25&,&39&,&56&,&\color{#20A900}{76}\\ \mbox{Second difference:}&&&8&,&11&,&14&,&17&,&\color{#20A900}{20}\\ \mbox{Third difference:}&&&&3&,&3&,&3&,&\color{#20A900}3 \end{array}

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Apply this method to polynomials and you'll get 0's at the end.

Apply this method to powers and you'll get the previous iteration after some time.

Kenny Lau - 6 years, 11 months ago
Nimesh Nair
Jun 17, 2014

The question is wrong..Instead of 75,it should be 85.. Then only can we reach a common difference of 3..

0 Helpful 0 Interesting 0 Brilliant 0 Confused

Yes it will 85 ..

Subham Agarwal - 6 years, 12 months ago

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