The sum of the infinite series 1+ 56+ 12 6^2 + 22 6^3 + 35 6^4 + 51 6^5 + 70 6^6 + is equal to

JEE Main Mathematics question

The sum of the infinite series is equal to

Answer: (C)

The numerators are the pentagonal numbers , so the sum is with .

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Question ID VK-022164