A367613 Numbers with exactly one comma-child.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 32, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 46, 47, 48, 49, 50, 51, 53, 55, 56, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 70, 73, 74, 75, 76, 77, 78, 79, 80, 82, 83

Offset: 1

Author

N. J. A. Sloane, Dec 15 2023

Keywords

• nonn
• base

Comments

Complement of union of A367341 and A367346.

See A367338 for definition of comma-child.

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..10000
• Eric Angelini, Michael S. Branicky, Giovanni Resta, N. J. A. Sloane, and David W. Wilson, The Comma Sequence: A Simple Sequence With Bizarre Properties, arXiv:2401.14346, Youtube

Crossrefs

Cf. A121895, A367341 (numbers with no comma-children), A367346 (numbers with two comma-children).

Programs

Mathematica

fQ[n_]:=Module[{k=n+10*Last[IntegerDigits[n]]+Range[9]},Length[Select[k,#-n==FromDigits[{Last[IntegerDigits[n]],First[IntegerDigits[#]]}]&]]]==1;
Select[Range[83],fQ[#]&] (* Ivan N. Ianakiev, Dec 16 2023 *)

Python

def ok(n):
    m = n + 10*(n%10)
    return len([m+y for y in range(1, 10) if int(str(m+y)[0]) == y]) == 1
print([k for k in range(1, 100) if ok(k)]) # Michael S. Branicky, Dec 28 2023