A387938 Fixed points of A390052.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 18, 19, 20, 21, 22, 23, 27, 29, 30, 31, 33, 40, 41, 42, 43, 44, 45, 46, 47, 51, 52, 53, 55, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 69, 71, 73, 77, 80, 82, 83, 84, 86, 87, 88, 89, 90, 93, 94, 97, 99, 101, 103, 109, 111, 122, 148, 151, 193

Offset

1,2

Comments

For every term t in A179239 there is exactly one anagram from t in this sequence. For example 13 is in A179239. It has anagrams 13 and 31. Of those anagrams 31 is in this sequence. - David A. Corneth, Oct 29 2025

Links

Paolo Xausa and Michael S. Branicky, Table of n, a(n) for n = 1..10000

Formula

A390052(a(n)) = a(n).

Mathematica

A387938Q[k_] := k == Last[SortBy[Map[FromDigits, Permutations[IntegerDigits[k]]], FactorInteger[#][[-1, 1]] &, Less]];
Select[Range[200], A387938Q]

Prog

(Python)
from sympy import factorint
from itertools import combinations_with_replacement as cwr, count, islice, permutations
def b(s): # A390052 with tuple of digits argument
    if s == ("1", ): return 1
    m, argm = 0, -1
    for p in permutations(sorted(s)):
        t = int("".join(p))
        f = 0 if t == 1 else max(factorint(t))
        if f > m: m, argm = f, t
    return argm
def agen(): # generator of terms
    for d in count(1):
        lb = 10**(d-1)
        yield from sorted(t for s in cwr("9876543210", d) if lb <= (t:=b(s)))
print(list(islice(agen(), 100)))

Crossrefs

Cf. A179239, A390052.

Sequence in context: A293448 A085079 A289234 * A033000 A130573 A032980

Adjacent sequences: A387935 A387936 A387937 * A387939 A387940 A387941

Keyword

nonn,base

Author

Paolo Xausa and Michael S. Branicky, Oct 29 2025

Status

approved