A078222 a(1) = 2, a(n+1) > a(n) is the smallest multiple of a(n) using only even digits.

2, 4, 8, 24, 48, 240, 480, 2400, 4800, 24000, 48000, 240000, 480000, 2400000, 4800000, 24000000, 48000000, 240000000, 480000000, 2400000000, 4800000000, 24000000000, 48000000000, 240000000000, 480000000000, 2400000000000

Offset

1,1

Comments

a(2n) = 24*10^(n-2), a(2n+1) = 48*10^(n-2) for n > 1.

Links

Table of n, a(n) for n=1..26.

Index entries for linear recurrences with constant coefficients, signature (0, 10).

Formula

From Chai Wah Wu, Nov 20 2019: (Start)

a(n) = 10*a(n-2) for n > 5.

G.f.: x*(32*x^4 + 16*x^3 + 12*x^2 - 4*x - 2)/(10*x^2 - 1). (End)

Mathematica

Join[{2, 4, 8}, Flatten[Table[{24, 48}10^n, {n, 0, 20}]]] (* Harvey P. Dale, May 01 2013 *)

Crossrefs

Cf. A078221.

Sequence in context: A334764 A218861 A359039 * A078223 A291405 A306420

Adjacent sequences: A078219 A078220 A078221 * A078223 A078224 A078225

Keyword

base,nonn

Author

Amarnath Murthy, Nov 23 2002

Extensions

More terms from Sascha Kurz, Jan 04 2003

Status

approved