A249182 Proceed counterclockwise on the outer keys of a numeric keypad (i.e., 1,2,3,6,9,8,7,4): first single digits, then concatenate two digits, then three, etc.

1, 2, 3, 6, 9, 8, 7, 4, 12, 23, 36, 69, 98, 87, 74, 41, 123, 236, 369, 698, 987, 874, 741, 412, 1236, 2369, 3698, 6987, 9874, 8741, 7412, 4123, 12369, 23698, 36987, 69874, 98741, 87412, 74123, 41236, 123698, 236987, 369874, 698741, 987412, 874123, 741236, 412369

Offset: 1

Author

M. F. Hasler, Oct 23 2014

Keywords

• nonn
• base

Comments

k-digit terms start at index 8k-7; for example, at index 57, start the 8-digit terms 12369874, 23698741, 36987412, 69874123, 98741236, 87412369, 74123698, 41236987.

Crossrefs

Cf. A059805, A091331, A091332, A249163.

Programs

PARI

d=Vec("12369874");for(L=1,6,for(i=1,#d,print1(concat(vector(L,j,d[(i+j-2)%#d+1]))",")))