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 A244965 Triangle read by rows: T(n,k) = sum of the k-th divisor island of n. 0
 1, 3, 1, 3, 3, 4, 1, 5, 6, 6, 1, 7, 3, 4, 8, 1, 3, 9, 3, 5, 10, 1, 11, 10, 6, 12, 1, 13, 3, 7, 14, 1, 3, 5, 15, 3, 4, 8, 16, 1, 17, 6, 6, 9, 18, 1, 19, 3, 9, 10, 20, 1, 3, 7, 21, 3, 11, 22, 1, 23, 10, 6, 8, 12, 24, 1, 5, 25, 3, 13, 26, 1, 3, 9, 27, 3, 4, 7, 14, 28 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A divisor island is any set of consecutive divisors of a number where no pairs of consecutive divisors in the set are separated by 2 or more. For the number of divisor islands of n see A137921. Row n has length A137921(n). Row sums give A000203. T(n,1) is a positive triangular number. LINKS FORMULA T(n,k) = A027750(n,k), if A137921(n) = A000005(n). EXAMPLE Written as an irregular triangle the sequence begins: 1; 3; 1, 3; 3, 4; 1, 5; 6, 6; 1, 7; 3, 4, 8; 1, 3, 9; 3, 5, 10; 1, 11; 10, 6, 12; 1, 13; 3, 7, 14; 1, 3, 5, 15; 3, 4, 8, 16; 1, 17; 6, 6, 9, 18; 1, 19; 3, 9, 10, 20; ... For n = 20 and k = 2 the divisors of 20 are [1, 2, 4, 5, 10, 20], there are four divisor islands: [1, 2], [4, 5], [10], [20] and the sum of the second divisor island is 4 + 5 = 9, so T(20,2) = 9. CROSSREFS Cf. A000203, A000217, A027750, A137921. Sequence in context: A211974 A136297 A243339 * A049996 A143908 A117572 Adjacent sequences:  A244962 A244963 A244964 * A244966 A244967 A244968 KEYWORD nonn,tabf AUTHOR Omar E. Pol, Jul 24 2014 STATUS approved

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Last modified March 26 16:33 EDT 2019. Contains 321510 sequences. (Running on oeis4.)