A004092 Sum of digits of even numbers.

0, 2, 4, 6, 8, 1, 3, 5, 7, 9, 2, 4, 6, 8, 10, 3, 5, 7, 9, 11, 4, 6, 8, 10, 12, 5, 7, 9, 11, 13, 6, 8, 10, 12, 14, 7, 9, 11, 13, 15, 8, 10, 12, 14, 16, 9, 11, 13, 15, 17, 1, 3, 5

Offset

0,2

Comments

a(n) >= A007953(n) / 5 with equality iff n is in A169964 (see Diophante link). - Bernard Schott, Apr 29 2023

Links

G. C. Greubel, Table of n, a(n) for n = 0..10000

Diophante, A1762, Des chiffres à la moulinette (in French).

Formula

a(n) = 2n - 9*Sum_{k=1..1+floor(log_10(2n))} floor( n/(5*10^(k-1)) ). - Anthony Browne, Jun 18 2016

a(n) = A007953(2n). - Alois P. Heinz, Apr 11 2018

Mathematica

Table[Sum[DigitCount[2*n][[i]]*i, {i, 9}], {n, 0, 100}] (* G. C. Greubel, Jun 19 2016 *)

Prog

(PARI) a(n)=sumdigits(2*n) \\ Charles R Greathouse IV, Jun 19 2016

Crossrefs

Cf. A007953, A169964.

Sequence in context: A146082 A169909 A180592 * A133311 A088402 A077492

Adjacent sequences: A004089 A004090 A004091 * A004093 A004094 A004095

Keyword

nonn,base,easy

Author

N. J. A. Sloane, Dec 11 1996

Status

approved