A336580 Numbers k such that A334676(k) = 1.

1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 15, 24, 25, 35, 36, 45, 48, 72, 75, 125, 135, 140, 144, 175, 216, 225, 250, 270, 280, 288, 375, 384, 432, 540, 625, 675, 864, 875, 1080, 1125, 1250, 1296, 1350, 1575, 1620, 1680, 1728, 1750, 1800, 1875, 1944, 2160, 2250, 2500

Offset: 1

Author

Rémy Sigrist, Jul 26 2020

Keywords

• nonn
• base

Comments

All terms are 7-smooth (A002473).

This sequence is infinite as it contains the powers of 5.

Examples

			Regarding the number 540:
- 540 / 4 = 135,
- 135 / 3 = 45,
- 45 / 5 = 9,
- 9 / 9 = 1,
- so A334676(540) = 1
- and 540 belongs to this sequence.
		

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10000
• Rémy Sigrist, Illustration of terms < 1000
• Rémy Sigrist, PARI program for A336580

Crossrefs

Cf. A000351, A002473, A334676.

Programs

PARI

for (n=1, #keep=vector(2500, n, n==1), if (keep[n], print1 (n ", "); for (d=2, min(9, #keep\n), if (setsearch (Set(digits(nd=n*d)), d), keep[nd]=1))))

PARI

See Links section.