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A256440
Regular triangle where the n-th row lists the integers k between 1 and n ordered by increasing value of sigma(k)/k where sigma is the sum of divisors, A000203.
4
1, 1, 2, 1, 3, 2, 1, 3, 2, 4, 1, 5, 3, 2, 4, 1, 5, 3, 2, 4, 6, 1, 7, 5, 3, 2, 4, 6, 1, 7, 5, 3, 2, 4, 8, 6, 1, 7, 5, 3, 9, 2, 4, 8, 6, 1, 7, 5, 3, 9, 2, 4, 10, 8, 6, 1, 11, 7, 5, 3, 9, 2, 4, 10, 8, 6, 1, 11, 7, 5, 3, 9, 2, 4, 10, 8, 6, 12, 1, 13, 11, 7, 5, 3, 9, 2, 4, 10, 8, 6, 12
OFFSET
1,3
LINKS
Michel Marcus, 100 rows
EXAMPLE
Triangle starts:
1;
1, 2;
1, 3, 2;
1, 3, 2, 4;
1, 5, 3, 2, 4;
1, 5, 3, 2, 4, 6;
1, 7, 5, 3, 2, 4, 6;
...
MATHEMATICA
f[n_] := Block[{t = Table[0, {n}], j, k}, For[j = 1, j <= n, j++, t[[j]] = {}; For[k = 1, k <= j, k++, AppendTo[t[[j]], DivisorSigma[1, k]/k]]]; Ordering /@ t]; f@ 13 // Flatten (* Michael De Vlieger, Mar 29 2015 *)
PROG
(PARI) lista(nn) = {for (n=1, nn, v = vector(n, k, sigma(k)/k); w = vecsort(v, , 1); for (k=1, n, print1(w[k], ", ")); print(); ); }
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Michel Marcus, Mar 29 2015
STATUS
approved