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 A273157 Numbers which have nonpositive entries in the difference table of their divisors (complement of A273130). 1
 6, 10, 12, 14, 15, 18, 20, 22, 24, 26, 28, 30, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, 50, 52, 54, 56, 58, 60, 62, 63, 66, 68, 70, 72, 74, 75, 76, 77, 78, 80, 82, 84, 86, 88, 90, 91, 92, 94, 96, 98, 99, 100, 102, 104, 105, 106, 108, 110, 112, 114, 116, 117 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primorial numbers (A002110) greater than 2 are in this sequence. LINKS Table of n, a(n) for n=1..62. EXAMPLE 30 is in this sequence because the difference table of the divisors of 30 is: [1, 2, 3, 5, 6, 10, 15, 30] [1, 1, 2, 1, 4, 5, 15] [0, 1, -1, 3, 1, 10] [1, -2, 4, -2, 9] [-3, 6, -6, 11] [9, -12, 17] [-21, 29] [50] PROG (Sage) def nsf(z): D = divisors(z) T = matrix(ZZ, len(D)) for m, d in enumerate(D): T[0, m] = d for k in range(m-1, -1, -1) : T[m-k, k] = T[m-k-1, k+1] - T[m-k-1, k] if T[m-k, k] <= 0: return True return False print([n for n in range(1, 100) if nsf(n)]) CROSSREFS Cf. A069059, A187202, A273102, A273103, A273109, A273130 (complement). Sequence in context: A100658 A182301 A069059 * A139587 A201463 A119313 Adjacent sequences: A273154 A273155 A273156 * A273158 A273159 A273160 KEYWORD nonn AUTHOR Peter Luschny, May 16 2016 STATUS approved

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Last modified June 14 23:20 EDT 2024. Contains 373401 sequences. (Running on oeis4.)