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

1,1

Links

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

Example

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

Prog

(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

Crossrefs

Cf. A061427-A061430. A069512 gives another version.

Cf. A028846.

Sequence in context: A073143 A066613 A074312 * A190045 A247035 A069512

Adjacent sequences: A061423 A061424 A061425 * A061427 A061428 A061429

Keyword

nonn,base,easy

Author

Amarnath Murthy, May 03 2001

Extensions

More terms from Erich Friedman, May 08 2001

Status

approved