A173821 - OEIS

A173821

The digital sum of a(n) is visible in the smallest a(n+1) not yet present in the sequence.

1, 10, 11, 2, 12, 3, 13, 4, 14, 5, 15, 6, 16, 7, 17, 8, 18, 9, 19, 100, 21, 23, 25, 27, 29, 110, 20, 22, 24, 26, 28, 101, 32, 35, 38, 111, 30, 31, 34, 37, 102, 33, 36, 39, 112, 40, 41, 45, 49, 113, 50, 51, 46, 103, 42, 56, 114, 60, 61, 47, 115, 57, 120, 43, 67, 130, 44, 48, 121

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

a(1) = 1, and for n > 1 a(n) is the smallest integer not yet present in the sequence such that the digital sum of a(n-1) is a substring of the decimal digits of a(n).

LINKS

Charles R Greathouse IV, Table of n, a(n) for n=1..10000

Eric Angelini, Visible DigitSums (sequence S)

E. Angelini, Visible DigitSums [Cached copy, with permission]

EXAMPLE

The digital sum of 1 is 1, so a(2) is the first unused number containing a "1", 10 (1 is already used). The digital sum of 10 is 1, so a(3) is the first unused number containing a "1", 11 (1 and 10 are already used)... The digital sum of 19 is 10, so a(20) is the first unused number containing a "10", 100 (10 is already used).

CROSSREFS

Cf. A173822, A173823

Sequence in context: A334676 A176998 A328752 * A101807 A248025 A303501

Adjacent sequences: A173818 A173819 A173820 * A173822 A173823 A173824

KEYWORD

base,nonn,look

AUTHOR

Charles R Greathouse IV and Eric Angelini, Mar 01 2010

STATUS

approved