130213domain: NAppears in sequencesDecimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 1,3,0,2.at n=5A037708Values of n for which the concatenations 1nn1, 3nn3, 7nn7 and 9nn9 are all primes.at n=13A102504Row sums of triangular table A138612.at n=29A166020