|
%I #22 May 15 2022 16:24:34
%S 4,6,8,9,10,12,14,15,16,18,20,21,22,24,25,27,28,30,32,33,35,36,40,42,
%T 44,45,48,49,50,54,55,56,60,63,64,66,70,72,75,77,80,81,84,88,90,96,98,
%U 99,100,105,108,110,112,120,121,125,126,128,132,135,140,144,147,150
%N Composite numbers with only palindromic prime factors.
%H Robert Israel, <a href="/A046349/b046349.txt">Table of n, a(n) for n = 1..3020</a>
%F A033620 INTERSECT A002808. - _R. J. Mathar_, Sep 09 2015
%p isA046349 := proc(n)
%p simplify(isA033620(n) and not isprime(n)) ;
%p end proc:
%p for n from 2 to 300 do
%p if isA046349(n) then
%p printf("%d,",n) ;
%p end if;
%p end do: # _R. J. Mathar_, Sep 09 2015
%t palQ[n_]:=Reverse[x=IntegerDigits[n]]==x; Select[Range[4,150],!PrimeQ[#]&&And@@palQ/@First/@FactorInteger[#]&] (* _Jayanta Basu_, Jun 05 2013 *)
%t Select[Range[200],CompositeQ[#]&&AllTrue[FactorInteger[#][[All,1]],PalindromeQ]&] (* _Harvey P. Dale_, May 15 2022 *)
%o (Python)
%o from sympy import isprime, primefactors
%o def pal(n): s = str(n); return s == s[::-1]
%o def ok(n): return not isprime(n) and all(pal(f) for f in primefactors(n))
%o print(list(filter(ok, range(4, 151)))) # _Michael S. Branicky_, Apr 06 2021
%Y Cf. A002385, A033620, A046350, A046351.
%K nonn,base,easy
%O 1,1
%A _Patrick De Geest_, Jun 15 1998
|
