A116280 n times n+3 gives the concatenation of two numbers m and m-1.
6, 77, 80918, 91808, 326509, 475024, 524974, 673489, 4323776, 4767131, 5232867, 5676222, 4083911140, 4975000249, 5024999749, 5916088858, 9503960495, 9604950395, 4186904462791, 4313465946774, 5686534053224, 5813095537207
Offset: 1