1,1

Nontrivial means that there must be at least two factors.

Ely Golden, Table of n, a(n) for n = 1..10000

Ely Golden, General program for generating vampire number sequences

175 is a member as 175 = 7 * 25 = 10101111_2 = 111_2 * 11001_2

5887 is a member as 5887 = 7 * 29 * 29 = 1011011111111_2 = 111_2 * 11101_2 * 11101_2

Cf. A020342

Sequence in context: A303811 A207146 A045260 * A192173 A093472 A270304

Adjacent sequences: A280964 A280965 A280966 * A280968 A280969 A280970

nonn,base

Ely Golden, Jan 11 2017

approved