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 A220848 a(n) = sum_(d|n) product_(d_x|n, d_x<=d) d_x. 1
 1, 3, 4, 11, 6, 45, 8, 75, 31, 113, 12, 1905, 14, 213, 244, 1099, 18, 6201, 20, 8451, 466, 509, 24, 346929, 131, 705, 760, 22803, 30, 839019, 32, 33867, 1126, 1193, 1266, 10374657, 38, 1485, 1564, 2627571, 42, 3189609, 44, 87219, 93304, 2165, 48, 260348721 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Conjecture: sequence is injective (all terms of this sequence occur only once). The conjecture is true for the first 100000 terms. - Harvey P. Dale, Dec 02 2017 LINKS Jaroslav Krizek, Table of n, a(n) for n = 1..100 FORMULA a(p) = p + 1 for prime p. EXAMPLE The divisors of 6 are 1, 2, 3, 6. a(n) = 1 + (1*2) + (1*2*3) + (1*2*3*6) = 1 + 2 + 6 + 36 = 45. MATHEMATICA f[x_]:=Module[{d=Divisors[x]}, Total[Table[Times@@Take[d, n], {n, Length[ d]}]]]; Array[f, 50] (* Harvey P. Dale, Dec 02 2017 *) CROSSREFS Sequence in context: A175317 A056045 A360794 * A232891 A096223 A232862 Adjacent sequences: A220845 A220846 A220847 * A220849 A220850 A220851 KEYWORD nonn,easy AUTHOR Jaroslav Krizek, Dec 22 2012 STATUS approved

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Last modified May 30 02:25 EDT 2023. Contains 363044 sequences. (Running on oeis4.)