A302563 Numbers whose digital root is equal to their number of digits.

1, 11, 20, 29, 38, 47, 56, 65, 74, 83, 92, 102, 111, 120, 129, 138, 147, 156, 165, 174, 183, 192, 201, 210, 219, 228, 237, 246, 255, 264, 273, 282, 291, 300, 309, 318, 327, 336, 345, 354, 363, 372, 381, 390, 399, 408, 417, 426, 435, 444

Offset

1,2

Comments

Last term is a(111111111) = 999999999. - Giovanni Resta, Aug 16 2018

Links

Table of n, a(n) for n=1..50.

Example

11 and 111 belong to the set as they both have the same number of digits as their digital root, respectively; 11 has two digits and also digital root two, and 111 has three digits and digital root three. 302563 does not belong to the set, since it has six digits and digital root one.

Mathematica

Select[Range[1000], IntegerLength[#] == Mod[#-1, 9] + 1 &] (* Giovanni Resta, Aug 16 2018 *)

Prog

(PARI) isok(n) = if(n, (n-1)%9+1) == #Str(n); \\ Michel Marcus, Aug 16 2018

Crossrefs

Cf. A010888, A055642, A098955.

Sequence in context: A038581 A044054 A044435 * A011753 A120442 A059407

Adjacent sequences: A302560 A302561 A302562 * A302564 A302565 A302566

Keyword

nonn,easy,fini,base

Author

Halfdan Skjerning, Aug 16 2018

Status

approved