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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 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Michel Marcus, Rows n = 1..100 of triangle, flattened 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 Cf. A000203, A247015, A247022. Sequence in context: A082074 A132283 A307081 * A088370 A328719 A113787 Adjacent sequences:  A256437 A256438 A256439 * A256441 A256442 A256443 KEYWORD nonn,tabl AUTHOR Michel Marcus, Mar 29 2015 STATUS approved

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Last modified April 15 06:12 EDT 2021. Contains 342975 sequences. (Running on oeis4.)