Upon the death of Saidie May in 1951, Jensen settled in New York and began to focus exclusively on painting, out of his Lincoln Arcade studio. Here he first gained the attention of James Johnson Sweeney, Director of the Guggenheim Museum. His first solo exhibition of twelve canvases was held in 1952 at the John Heller Gallery,including portraits, still life, landscapes and figures in an abstract expressionist style, influenced by his studies of Goethe's color theory, with a palette of prismatic colors.Around this time, he began what would be long friendships with painter Mark Rothko and art critic Lil Picard. This was followed by his first solo show at the Tanager Gallery in 1955, the same year he began to exchange ideas with Sam Francis.In 1957, he started to incorporate checkerboards in his prismatic colored murals, and in diagrams and paintings on paper. He also began to investigate his compositional logic, including calligraphy, and became extremely prolific. Henry Luce III, son of the founder of Time Magazine, first collected his work, eventually commissioning a mural for the Time/Life building in Paris in 1959.
By the mid 1970s, he became interested in ancient number systems, magnetism and planetary effects on seasons, which became themes of his subsequent paintings.Wikipedia