323131domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumber of planar n X n X n binary triangular grids with mirror symmetry about one altitude with no more than 8 ones in any 5 X 5 X 5 subtriangle.at n=8A153963Pseudoprimes to base 5, written in base 5.at n=20A262102Prime numbersat n=27859