A355848 - OEIS

%I #27 Sep 15 2022 09:19:59

%S 1,3,5,6,7,0,11,14,15,13,20,21,17,22,30,19,27,0,23,33,35,42,45,39,44,

%T 60,29,38,54,56,31,0,46,51,55,66,70,37,49,57,41,65,68,78,96,43,0,47,

%U 62,69,77,105,0,99,126,53,85,102,110,91,92,132,140,0,59,87,95,114,135,168

%N Irregular triangle read by rows in which row n lists the numbers whose divisors have arithmetic mean n, or 0 if no such number exists.

%e Triangle begins:

%e   n=1: 1;

%e   n=2: 3;

%e   n=3: 5, 6;

%e   n=4: 7;

%e   n=5: 0;

%e   n=6: 11, 14, 15;

%e   n=7: 13, 20;

%e   n=8: 21;

%e   n=9: 17, 22, 30;

%e   ...

%t nmax=30; a={}; For[n=1, n<=nmax, n++, nok=0; For[k=1, k<=n(n+1)/2, k++, If[DivisorSum[k,#&]==n*DivisorSigma[0,k], AppendTo[a,k]; nok=1]]; If[nok==0, AppendTo[a,0]]]; a (* _Stefano Spezia_, Jul 20 2022 *)

%Y Cf. A162538 (left border).

%Y Cf. A000005, A000203, A003601, A157847, A324990, A324991.

%K nonn,tabf

%O 1,2

%A _Mohammed Yaseen_, Jul 20 2022