5668705domain: NAppears in sequencesPierpont 4-almost primes: numbers with exactly 4 prime divisors, not necessarily distinct, of the form 2^K*3^L + 1.at n=18A111344Number of (n+2) X (1+2) 0..1 arrays with each 3 X 3 subblock having clockwise perimeter pattern 00010001 00010101 or 01010101.at n=23A261106