A046349 Composite numbers with only palindromic prime factors.

4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 27, 28, 30, 32, 33, 35, 36, 40, 42, 44, 45, 48, 49, 50, 54, 55, 56, 60, 63, 64, 66, 70, 72, 75, 77, 80, 81, 84, 88, 90, 96, 98, 99, 100, 105, 108, 110, 112, 120, 121, 125, 126, 128, 132, 135, 140, 144, 147, 150

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..3020

Formula

A033620 INTERSECT A002808. - R. J. Mathar, Sep 09 2015

Maple

isA046349 := proc(n)
    simplify(isA033620(n) and not isprime(n)) ;
end proc:
for n from 2 to 300 do
    if isA046349(n) then
        printf("%d, ", n) ;
    end if;
end do: # R. J. Mathar, Sep 09 2015

Mathematica

palQ[n_]:=Reverse[x=IntegerDigits[n]]==x; Select[Range[4, 150], !PrimeQ[#]&&And@@palQ/@First/@FactorInteger[#]&] (* Jayanta Basu, Jun 05 2013 *)
Select[Range[200], CompositeQ[#]&&AllTrue[FactorInteger[#][[All, 1]], PalindromeQ]&] (* Harvey P. Dale, May 15 2022 *)

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(4, 151)))) # Michael S. Branicky, Apr 06 2021

Crossrefs

Cf. A002385, A033620, A046350, A046351.

Sequence in context: A340058 A174891 A051035 * A115683 A175526 A192506

Adjacent sequences: A046346 A046347 A046348 * A046350 A046351 A046352

Keyword

nonn,base,easy

Author

Patrick De Geest, Jun 15 1998

Status

approved