A097387 Let f(x)=(largest digit of x)^(smallest digit of x) + x (A097385). Sequence gives numbers n such that f(n) and f(n+1) are both prime.

60, 460, 640, 820, 1360, 1480, 1620, 1870, 2110, 2380, 3460, 3630, 3880, 4560, 4650, 5640, 5650, 5860, 6210, 6310, 6360, 6420, 7480, 8170, 8680, 8830, 11680, 11830, 12280, 12640, 12820, 13780, 14620, 15460, 15640, 15660, 15880, 16410, 16420

Offset: 1

Author

Jason Earls, Aug 18 2004

Keywords

• base
• easy
• nonn

Comments

Conjecture: Terms will always be multiples of ten. Aug 21, 2004: Dean Hickerson proved this.

Examples

			640 is in the sequence because 6^0 + 640 = 641 and 6^1 + 641 = 647, both prime.
		

Crossrefs

Cf. A054054, A054055, A097385, A097386.