395507653domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumber of 2 X n 0..1 arrays with every element both equal and not equal to some elements at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero.at n=19A278281Prime numbersat n=21109480