Born into a family Inyakino Ryazan region Shilovsky district, on 23 December 1920. The love of painting developed from childhood. Contributed to this beautiful nature, landscapes and architecture of the native land of the artist.
In 1953 Nikolai Sergeyevich entered the Ryazan art College. He learned from such wonderful teachers as Kurakin and Serov, who opened the way for him in the future. Young and talented artist did not stop there and after graduating in 1956, he entered the Moscow state correspondence pedagogical Institute, where he studied from 1957 to 1962.
Mamontov taught at the Ryazan art College from 1956 to 1982, drawing and sketching. Denisov repeatedly was the participant of city, regional and Republican exhibitions. His work captivating the viewer with its vibrant colors. Especially good was his landscapes "Morning", "the March snow", "Rye". All the paintings glorified the beauty and grandeur of Russian nature. He died in 1987. in Ryazan.