Thomas D. Seidenberg, 76, of Peterborough, NH passed away peacefully on April 8, 2026 after a lengthy battle with cancer.

Although he has maintained a lifelong love of his birthplace, Philadelphia, Tom grew up in the Bay Area. It was there he developed a love of basketball, baseball, and Dungeness crab. He graduated from Redwood High School in San Rafael, CA and got his degree in Geology from Whitworth College in Spokane, WA. Soon after, he began teaching and coaching in Leavenworth, WA, and, eventually, at Eisenhower High School in Yakima, WA. While in Yakima, he pursued a Master’s in Math at Central Washington University, coached tennis and basketball, and raised two children. In 1987, he was awarded the Presidential Award for Excellence in Mathematics Teaching.

For many years, he spent his summers traveling all over the United States to conduct workshops for secondary school math teachers. These travels ultimately led him to a position teaching math at Phillips Exeter Academy in Exeter, NH. During his 29 years at Exeter, he taught, coached, and mentored thousands of students. He was well-known for his sense of humor, his patience, and his ability to connect with students. His high-quality teaching was recognized through multiple awards and titles throughout his tenure. In addition to teaching and coaching basketball, he was the director of the Anya S. Greer Conference on Mathematics & Technology for 25 years. He was an advocate for teachers, particularly public school teachers with limited resources, and believed teachers learn best from other teachers. Over the years, he traveled around the world to share his knowledge of math and technology at schools and conferences.

It’s hard to believe there was time for anything else, but Tom made good use of his downtime. He frequently traveled to Colombia, France, Scotland, Egypt, Israel, and many other places to satisfy his interest in people and places. While there, he walked thousands of miles and took hundreds of photos. In addition to his travels, Tom spent his retirement reading, biking, walking on the beach, finding good Mexican food, watching March Madness, attending Spring training, and following the many, many adventures of his young granddaughters.

Tom was predeceased by his parents and his brother. He is also predeceased by his wife, Lynn M. Seidenberg, who died of cancer in 2009, and his wife, Anne L. Surman, who died of cancer in 2022. Tom is survived by his children, Nathan Seidenberg of Lakeville, CT and Anne (Seidenberg) Pinard and her husband, Tom, of Sullivan, NH, and two granddaughters.

For those who wish to make a donation in Tom’s honor, gifts may be made in his name to Dog Mountain in St. Johnsbury, VT, or to the Staff Appreciation Fund at Rivermead in Peterborough, NH. Services have not yet been planned.