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

1,2

Links

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

Example

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

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 *)

Crossrefs

Cf. A276465, A276655, A276699.

Sequence in context: A217150 A274178 A118578 * A181781 A324551 A338081

Adjacent sequences: A276697 A276698 A276699 * A276701 A276702 A276703

Keyword

nonn,base

Author

Paolo P. Lava, Sep 15 2016

Status

approved