A356520 Numbers k such that A000005(A007953(k)) = A007953(k).

1, 2, 10, 11, 20, 100, 101, 110, 200, 1000, 1001, 1010, 1100, 2000, 10000, 10001, 10010, 10100, 11000, 20000, 100000, 100001, 100010, 100100, 101000, 110000, 200000, 1000000, 1000001, 1000010, 1000100, 1001000, 1010000, 1100000, 2000000, 10000000, 10000001

Offset

1,2

Comments

Union of A011557 and A052216. I.e., numbers with digital sum 1 or 2. - David A. Corneth, Aug 10 2022

Links

Table of n, a(n) for n=1..37.

Example

k = 101; A000005(A007953(101)) = A007953(101) = 2, thus k = 101 is in the sequence.

Mathematica

Select[Range[1, 10000001], Plus @@ IntegerDigits[#] < 3 &] (* Amiram Eldar, Aug 10 2022 *)

Prog

(PARI) isok(k) = my(s=sumdigits(k)); numdiv(s) == s; \\ Michel Marcus, Aug 10 2022
(PARI) is(n) = my(s = sumdigits(n)); s == 1 || s == 2 \\ David A. Corneth, Aug 10 2022
(Python)
from itertools import count, islice
def agen():
    for i in count(0):
        yield from [10**i] + [10**i + 10**j for j in range(i+1)]
print(list(islice(agen(), 37))) # Michael S. Branicky, Aug 10 2022

Crossrefs

Cf. A000005, A007953, A011557, A052216, A101318, A306509, A356061.

Sequence in context: A051373 A131096 A069263 * A174569 A179884 A174570

Adjacent sequences: A356517 A356518 A356519 * A356521 A356522 A356523

Keyword

nonn,easy,base

Author

Ctibor O. Zizka, Aug 10 2022

Status

approved