A046891 Values of n where number of permutations of digits a(n) that are prime increases.
1, 2, 13, 103, 107, 1007, 1013, 1049, 1079, 1237, 10013, 10039, 10079, 10139, 10237, 10279, 10379, 13789, 100127, 100139, 100235, 100237, 100279, 101237, 101239, 102347, 102367, 102379, 103579, 103789, 1001234, 1001237, 1001239, 1002347, 1002359, 1002367, 1002379
Offset: 1
Links
- Michael S. Branicky, Table of n, a(n) for n = 1..91
Programs
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Mathematica
ap[n_] := Count[FromDigits /@ Permutations[IntegerDigits[n]], ?PrimeQ]; t = {1}; x = 0; Do[If[ap[i] > x, AppendTo[t, i]; x = ap[i]], {i, 105000}]; t (* _Jayanta Basu, Jun 29 2013 *)
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Python
from sympy import prime from gmpy2 import is_prime from sympy.utilities.iterables import multiset_permutations as mp from itertools import count, islice, combinations_with_replacement as mc def f(n): return sum(1 for p in mp(str(n)) if is_prime(t:=int("".join(p)))) def bgen(d): for f in "123456789": yield from map(int, (f+"".join(m) for m in mc("0123456789", d-1))) def agen(): record = -1 for d in count(1): for k in bgen(d): v = f(k) if v > record: record = v yield k print(list(islice(agen(), 30))) # Michael S. Branicky, Feb 17 2024
Extensions
a(35) and beyond from Michael S. Branicky, Feb 17 2024