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 A305995 Rectangular array read by downward antidiagonals; row n consists of the numbers m such that n is the denominator of d(k)/d(1) + d(k-1)/d(2) + ... + d(k)/d(1), where d(1),d(2),...,d(k) are the unitary divisors of m. 6
 1, 10, 2, 65, 68, 3, 130, 520, 6, 4, 260, 1768, 15, 40, 5, 340, 2600, 30, 104, 50, 12, 1105, 6760, 60, 1040, 1700, 120, 7, 1972, 17680, 150, 20560, 3250, 312, 14, 8, 2210, 62600, 195, 35360, 7825, 600, 35, 2080, 9, 4420, 165896, 204, 85280, 27625, 3120, 70, 4112, 18, 20 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Every positive integer occurs exactly once, so that as a sequence, this is a permutation of the positive integers. The numbers in row n are divisible by n; see A305996 for the quotients. LINKS EXAMPLE Northwest corner:    1    10    65   130    260     340    1105    2    68   520  1768   2600    6760   17680    3     6    15    30     60     150     195    4    40   104  1040  20560   35360   85280    5    50  1700  3250   7825   27625   31300   12   120   312   600   3120   61680  106080    7    14    35    70    140     175     350    8  2080  4112  6560  32800   38048   52000    9    18    90   369    585     612     738 MATHEMATICA t[n_] := Table[r[n][[k[n] + 1 - i]]/r[n][[k[1] + i - 1]], {i, 1, k[n]}]; s = Table[Total[t[n]], {n, 1, z}]; a[n_] := If[IntegerQ[s[[n]]], 1, 0]; d = Denominator[s]; row[n_] := Flatten[Position[d, n]] TableForm[Table[row[n], {n, 1, 10}]]  (* A305995 array *) r1[n_, k_] := row[n][[k]]; zz = 10; Flatten[Table[r1[n - k + 1, k], {n, zz}, {k, n, 1, -1}]]  (* A305995 sequence *) CROSSREFS Cf. A077610, A229994, A229996, A229997, A229998, A229998, A305996. Sequence in context: A232590 A094715 A213555 * A096043 A001202 A054841 Adjacent sequences:  A305992 A305993 A305994 * A305996 A305997 A305998 KEYWORD nonn,tabl AUTHOR Clark Kimberling, Jun 16 2018 STATUS approved

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Last modified May 8 06:18 EDT 2021. Contains 343653 sequences. (Running on oeis4.)