A061426 Geometric mean of the digits = 2. In other words, the product of the digits is = 2^k where k is the number of digits.

2, 14, 22, 41, 118, 124, 142, 181, 214, 222, 241, 412, 421, 811, 1128, 1144, 1182, 1218, 1224, 1242, 1281, 1414, 1422, 1441, 1812, 1821, 2118, 2124, 2142, 2181, 2214, 2222, 2241, 2412, 2421, 2811, 4114, 4122, 4141, 4212, 4221, 4411, 8112, 8121, 8211

Offset: 1

Author

Amarnath Murthy, May 03 2001

Keywords

• nonn
• base
• easy

Examples

			124 is a term as the geometric mean of digits is (1*2*4) = 8 = 2^3.
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A061427-A061430. A069512 gives another version.

Cf. A028846.

Programs

Haskell

a061426 n = a061426_list !! (n-1)
a061426_list = g [1] where
   g ds = if product ds == 2 ^ length ds
          then foldr (\d v -> 10 * v + d) 0 ds : g (s ds) else g (s ds)
   s [] = [1]; s (8:ds) = 1 : s ds; s (d:ds) = 2*d : ds
-- Reinhard Zumkeller, Jan 13 2014

Extensions

More terms from Erich Friedman, May 08 2001