A276700 - OEIS

%I #9 Apr 02 2020 18:00:53

%S 1,21,25,30,32,36,392,441,525,560,625,630,672,750,756,800,900,960,979,

%T 1024,1080,1152,1215,1296,1411,1458,1463,1547,1742,1947,2059,2090,

%U 2210,2318,2405,2419,2444,2491,2508,2552,2652,2703,2871,2886,2924,2945,3116,3128

%N Numbers n such that Sum_{p|n} 0.p is an integer where p ranges over the prime divisors, with multiplicity, of n.

%H Paolo P. Lava, <a href="/A276700/b276700.txt">Table of n, a(n) for n = 1..1000</a>

%e 21 = 3 * 7 and 0.3 + 0.7 = 1;

%e 3128 = 2^3 * 17 * 23 and 3*0.2 + 0.17 + 0.23 = 1.

%p with(numtheory): P:= proc(q) local a,k,n;

%p for n from 1 to q do a:=ifactors(n)[2];

%p if type(add(a[k][2]*a[k][1]/10^(ilog10(a[k][1])+1),k=1..nops(a)),integer)

%p then print(n); fi; od; end: P(10^9);

%t paiQ[n_]:=IntegerQ[Total[#/10^IntegerLength[#]&/@Flatten[Table[#[[1]], #[[2]]]&/@ FactorInteger[n]]]]; Join[{1},Select[Range[3200],paiQ]] (* _Harvey P. Dale_, Apr 02 2020 *)

%Y Cf. A276465, A276655, A276699.

%K nonn,base

%O 1,2

%A _Paolo P. Lava_, Sep 15 2016