A276700 Numbers n such that Sum_{p|n} 0.p is an integer where p ranges over the prime divisors, with multiplicity, of n.

1, 21, 25, 30, 32, 36, 392, 441, 525, 560, 625, 630, 672, 750, 756, 800, 900, 960, 979, 1024, 1080, 1152, 1215, 1296, 1411, 1458, 1463, 1547, 1742, 1947, 2059, 2090, 2210, 2318, 2405, 2419, 2444, 2491, 2508, 2552, 2652, 2703, 2871, 2886, 2924, 2945, 3116, 3128

Offset: 1

Author

Paolo P. Lava, Sep 15 2016

Keywords

• nonn
• base

Examples

			21 = 3 * 7 and 0.3 + 0.7 = 1;
3128 = 2^3 * 17 * 23 and 3*0.2 + 0.17 + 0.23 = 1.
		

Links

• Paolo P. Lava, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A276465, A276655, A276699.

Programs

Maple

with(numtheory): P:= proc(q) local a,k,n;
for n from 1 to q do a:=ifactors(n)[2];
if type(add(a[k][2]*a[k][1]/10^(ilog10(a[k][1])+1),k=1..nops(a)),integer)
then print(n); fi; od; end: P(10^9);

Mathematica

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