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Shyam Sunder Gupta is a former senior officer of the Government of India and spearheaded multiple complex projects as Principal Chief Engineer of Indian Railways. He is an Indian Railway Service of Engineers (IRSE) officer of batch 1981. He has more than 35 years of experience in various managerial, administrative and technical positions, such as Principal Chief Engineer, Executive Director and Divisional Railway Manager on Indian Railways. An Indian recreational mathematician who is actively involved in popularising mathematics at the national and international levels. His major discoveries are Equal Product of Reversible Numbers (EPRNs), rare numbers, unique numbers, palindromic pseudoprimes, fifth-order prime polynomial, 17350-digit memorable prime, etc.
His interest in number recreations dates back to 1978, when his first paper, Miracles of Last Digit, was published. Since then, his contributions have been published in Science Reporter, Science Today, Math Education, At Right Angles, The American Mathematical Monthly, The Mathematical Gazette, Mathematical Spectrum, Scientia Magna and several international books like Unsolved Problems in Number Theory (by R. K. Guy), The Universal Book of Mathematics (by David J. Darling), The Penguin Dictionary of Curious and Interesting Numbers (by David Wells), Prime Curios!: The Dictionary of Prime Number Trivia (by Chris K. Caldwell and G. L. Honaker) and Those Fascinating Numbers (by Jean-Marie De Koninck). Author of the book, Creative Puzzles to Ignite Your Mind (Springer, 2023), he also co-authored Civil Engineering Through Objective Type Questions (CBS, 1985).
You may return most new, unopened items within 30 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
We can ship to virtually any address in the world. Note that there are restrictions on some products, and some products cannot be shipped to international destinations.
When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.
Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.
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