50513domain: NPropertiesPrimalityPrimeyesAppears in sequencesNoncomposite numbers in the southern ray of the Ulam spiral as oriented on the March 1964 cover of Scientific American.at n=28A168027k such that 0 = Sum_{j=1..k} A373223(k, j). The indices of the rows in Gauss's triangle with vanishing row sums.at n=28A373181Prime numbersat n=5181