A046350 Odd composite numbers with only palindromic prime factors.

9, 15, 21, 25, 27, 33, 35, 45, 49, 55, 63, 75, 77, 81, 99, 105, 121, 125, 135, 147, 165, 175, 189, 225, 231, 243, 245, 275, 297, 303, 315, 343, 363, 375, 385, 393, 405, 441, 453, 495, 505, 525, 539, 543, 567, 573, 605, 625, 655, 675, 693, 707, 729, 735, 755

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

palQ[n_]:=Reverse[x=IntegerDigits[n]]==x; Select[Range[9, 755, 2], !PrimeQ[#]&&And@@palQ/@First/@FactorInteger[#]&] (* Jayanta Basu, Jun 05 2013 *)
Select[Range[9, 800, 2], CompositeQ[#]&&AllTrue[FactorInteger[#][[All, 1]], PalindromeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 08 2018 *)

Prog

(Python)
from sympy import isprime, primefactors
def pal(n): s = str(n); return s == s[::-1]
def ok(n): return not isprime(n) and all(pal(f) for f in primefactors(n))
print(list(filter(ok, range(9, 756, 2)))) # Michael S. Branicky, Apr 06 2021

Crossrefs

Cf. A002385, A033620, A046349, A046351.

Sequence in context: A155474 A100819 A046446 * A225438 A175076 A046337

Adjacent sequences: A046347 A046348 A046349 * A046351 A046352 A046353

Keyword

nonn,base

Author

Patrick De Geest, Jun 15 1998

Status

approved