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A046348 Composite palindromes divisible by the sum of their prime factors (counted with multiplicity). 3

%I #30 May 02 2018 09:29:47

%S 4,646,2772,5445,8778,30303,48384,50505,54145,63336,77077,117711,

%T 219912,234432,239932,255552,272272,294492,535535,585585,636636,

%U 717717,825528,888888,951159,999999,1103011,1112111,1345431,2248422,2267622

%N Composite palindromes divisible by the sum of their prime factors (counted with multiplicity).

%H David A. Corneth, <a href="/A046348/b046348.txt">Table of n, a(n) for n = 1..4180</a> (Terms <= 10^15. First 1000 terms from R. J. Mathar and Giovanni Resta)

%H David A. Corneth, <a href="/A046348/a046348.gp.txt">PARI prog</a>

%e a(2)=646 : 2*17*19 -> 2 + 17 + 19 = 38 and 646 / 38 = 17.

%t t={}; Do[If[!PrimeQ[n]&&Reverse[x=IntegerDigits[n]]==x&&IntegerQ[n/Total[Times@@@FactorInteger[n]]],AppendTo[t,n]],{n,4,2.5*10^6}]; t (* _Jayanta Basu_, Jun 04 2013 *)

%t cpdQ[n_]:=CompositeQ[n]&&PalindromeQ[n]&&Divisible[n,Total[ Flatten[ Table[ #[[1]],#[[2]]]&/@FactorInteger[n]]]]; Select[Range[23*10^5],cpdQ] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 01 2018 *)

%o (PARI) See PARI link.

%Y Cf. A002113, A001414, A046346, A046347.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, Jun 15 1998

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