A169805 Twice the sum of the digits of n.

0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 14, 16, 18, 20, 22, 24, 26

Offset: 0

Author

N. J. A. Sloane, May 24 2010

Keywords

• nonn
• base

Comments

The only n such that a(n) = n are 0 and 18.

Links

• Erich Friedman, What's Special About This Number?

Crossrefs

Cf. A007953.

Programs

Mathematica

2*Total[IntegerDigits[#]]&/@Range[0,80] (* Harvey P. Dale, Apr 17 2022 *)

Formula

a(n) = 2*A007953(n).