A044438 Numbers n such that string 1,2 occurs in the base 3 representation of n but not of n+1.

5, 17, 23, 32, 53, 59, 71, 77, 86, 98, 104, 113, 161, 167, 179, 185, 194, 215, 221, 233, 239, 248, 260, 266, 275, 296, 302, 314, 320, 329, 341, 347, 356, 485, 491, 503, 509, 518, 539, 545, 557, 563, 572, 584, 590, 599, 647, 653