A329764 a(1) = 1; thereafter a(n+1) > a(n) is the smallest multiple of a(n) using only odd digits but not divisible by 9.

1, 3, 15, 75, 375, 9375, 159375, 71559375, 1195399359375, 353915911333359375, 51915571117579153359375, 753315397517553377717399173359375, 3319771735775931191533111595353537393933359375

Offset: 1

Author

Chai Wah Wu, Dec 04 2019

Keywords

• nonn
• base

Comments

Equivalently, the sequence is defined as a(1) = 1, a(2) = 3, a(3) = 15, and for n > 2, a(n+1) > a(n) is the smallest multiple of a(n) using only odd digits. All terms besides a(1) and a(2) are divisible by 5.

Crossrefs

Cf. A329762, A078221, A078223.