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A355848
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.
0
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, 60, 29, 38, 54, 56, 31, 0, 46, 51, 55, 66, 70, 37, 49, 57, 41, 65, 68, 78, 96, 43, 0, 47, 62, 69, 77, 105, 0, 99, 126, 53, 85, 102, 110, 91, 92, 132, 140, 0, 59, 87, 95, 114, 135, 168
OFFSET
1,2
EXAMPLE
Triangle begins:
n=1: 1;
n=2: 3;
n=3: 5, 6;
n=4: 7;
n=5: 0;
n=6: 11, 14, 15;
n=7: 13, 20;
n=8: 21;
n=9: 17, 22, 30;
...
MATHEMATICA
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 *)
CROSSREFS
Cf. A162538 (left border).
Sequence in context: A123572 A244953 A076819 * A181757 A181753 A082218
KEYWORD
nonn,tabf
AUTHOR
Mohammed Yaseen, Jul 20 2022
STATUS
approved