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 A272025 Irregular triangle read by rows, n>=1, 1<=k<=A038548(n), in which T(n,k) is the sum of the k-th pair of conjugate divisors of n, or T(n,k) is the central divisor of n if such pair does not exist. 0
 1, 3, 4, 5, 2, 6, 7, 5, 8, 9, 6, 10, 3, 11, 7, 12, 13, 8, 7, 14, 15, 9, 16, 8, 17, 10, 4, 18, 19, 11, 9, 20, 21, 12, 9, 22, 10, 23, 13, 24, 25, 14, 11, 10, 26, 5, 27, 15, 28, 12, 29, 16, 11, 30, 31, 17, 13, 11, 32, 33, 18, 12, 34, 14, 35, 19, 36, 12, 37, 20, 15, 13, 6, 38, 39, 21, 40, 16, 41, 22, 14, 13, 42, 43, 23, 17, 13 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE Triangle begins: 1; 3; 4; 5, 2; 6; 7, 5; 8; 9, 6; 10, 3; 11, 7; 12; 13, 8, 7; ... For n = 9 the divisors of 9 are [1, 3, 9]. There is only one pair of conjugate divisors: [1, 9], and the central divisor is 3, so the 9th row of triangle is [10, 3]. For n = 12 the divisors of 12 are [1, 2, 3, 4, 6, 12]. There are three pairs of conjugate divisors, they are [1, 12], [2, 6], [3, 4], so the 12th row of triangle is [13, 8, 7]. CROSSREFS Row sums give A000203. Row lengths give A038548. Right border gives A207376. Column 1 is A065475. Cf. A027750, A210959, A228814. Sequence in context: A239639 A099816 A237273 * A262411 A280488 A250072 Adjacent sequences:  A272022 A272023 A272024 * A272026 A272027 A272028 KEYWORD nonn,tabf AUTHOR Omar E. Pol, Apr 21 2016 STATUS approved

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Last modified July 23 11:44 EDT 2019. Contains 325254 sequences. (Running on oeis4.)