|
%I #11 Aug 14 2021 15:49:42
%S 18,144,150,168,175,198,220,230,242,246,255,322,366,444,624,1166,1243,
%T 1323,1330,1331,1462,1480,1530,1992,2187,2230,2240,2406,2436,2625,
%U 2650,2673,2730,2744,2808,2925,3024,3125,3182,3264,3286,3366,3388,3420,3484
%N Numbers n such that the sum of the prime factors of n (counted with multiplicity) is a proper substring of n.
%C "Proper" is needed in the definition to exclude 4 and all primes.
%e a(3)=144=2*2*2*2*3*3 and 2+2+2+2+3+3=14 and 14 is a substring of 144.
%t pfQ[n_]:=Module[{x=Total[Times@@@FactorInteger[n]],idx},idx=IntegerDigits[x];MemberQ[Partition[IntegerDigits[n],Length[idx],1],idx]&&x!=n]
%t Select[Range[0,3500],pfQ] (* _Harvey P. Dale_, Feb 09 2011 *)
%o (Python)
%o from sympy import factorint, isprime
%o A143992_list = [n for n in range(2,10**6) if n != 4 and not isprime(n) and str(sum(a*b for a, b in factorint(n).items())) in str(n)] # _Chai Wah Wu_, Aug 14 2021
%K base,nonn
%O 1,1
%A _Gil Broussard_, Sep 07 2008
%E Corrected by Harvey P. Dale, Feb 09 2011
|
