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 A143235 Triangle read by rows: T(n,k) = tau(n)*tau(k), the product of the number of divisors. 2
 1, 2, 4, 2, 4, 4, 3, 6, 6, 9, 2, 4, 4, 6, 4, 4, 8, 8, 12, 8, 16, 2, 4, 4, 6, 4, 8, 4, 4, 8, 8, 12, 8, 16, 8, 16, 3, 6, 6, 9, 6, 12, 6, 12, 9, 4, 8, 8, 12, 8, 16, 8, 16, 12, 16, 2, 4, 4, 6, 4, 8, 4, 8, 6, 8, 4, 6, 12, 12, 18, 12, 24, 12, 24, 18, 24, 12, 36, 2, 4, 4, 6, 4, 8, 4, 8, 6, 8, 4, 12, 4 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The triangle can also be created by the triple matrix product A130209 * A000012 * A130209. LINKS Table of n, a(n) for n=1..91. FORMULA T(n,k) = A000005(n)*A000005(k), 1<=k<=n. EXAMPLE First few rows of the triangle = 1; 2, 4; 2, 4, 4; 3, 6, 6, 9; 2, 4, 4, 6, 4; 4, 8, 8, 12, 8, 16; 2, 4, 4, 6, 4, 8, 4; 4, 8, 8, 12, 8, 16, 8, 16; 3, 6, 6, 9, 6, 12, 6, 12, 9; ... T(9,6) = 12 = d(9)*d(6) = 3*4. CROSSREFS Cf. A000005, A143236 (row sums). Sequence in context: A004020 A363290 A246436 * A069465 A047947 A018838 Adjacent sequences: A143232 A143233 A143234 * A143236 A143237 A143238 KEYWORD nonn,tabl,easy AUTHOR Gary W. Adamson, Aug 01 2008 STATUS approved

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Last modified October 3 17:33 EDT 2023. Contains 365870 sequences. (Running on oeis4.)