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 A210208 Triangle read by rows in which row n lists the divisors of n that are prime powers, A000961. 9
 1, 1, 2, 1, 3, 1, 2, 4, 1, 5, 1, 2, 3, 1, 7, 1, 2, 4, 8, 1, 3, 9, 1, 2, 5, 1, 11, 1, 2, 3, 4, 1, 13, 1, 2, 7, 1, 3, 5, 1, 2, 4, 8, 16, 1, 17, 1, 2, 3, 9, 1, 19, 1, 2, 4, 5, 1, 3, 7, 1, 2, 11, 1, 23, 1, 2, 3, 4, 8, 1, 5, 25, 1, 2, 13, 1, 3, 9, 27, 1, 2, 4, 7 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS A073093(n) = length of n-th row; A023888(n) = sum of n-th row; A183091(n) = product of n-th row; A034699(n) = T(n,A073093(n)) = maximum of n-th row; {T(n,k):k=1..A073093(n)} subset of {A027750(n,k):k=1..A000005(n)} for all n. LINKS Reinhard Zumkeller, Rows n=1..5000 of triangle, flattened Eric Weisstein's World of Mathematics, Divisor EXAMPLE 1; 1, 2; 1, 3; 1, 2, 4; 1, 5; 1, 2, 3; 1, 7; 1, 2, 4, 8; 1, 3, 9; 1, 2, 5; 1, 11; 1, 2, 3, 4; - Geoffrey Critzer, Feb 08 2015 MATHEMATICA Table[Prepend[Select[Divisors[n], PrimeNu[#] == 1 &], 1], {n, 1, 10}]//Grid (* Geoffrey Critzer, Feb 08 2015 *) PROG (Haskell) a210208 n k = a210208_tabf !! (n-1) !! (n-1) a210208_row n = a210208_tabf !! (n-1) a210208_tabf = map (filter ((== 1) . a010055)) a027750_tabf CROSSREFS Cf. A010055, A141809. Sequence in context: A222818 A057059 A169896 * A162306 A233773 A027750 Adjacent sequences:  A210205 A210206 A210207 * A210209 A210210 A210211 KEYWORD nonn,tabf AUTHOR Reinhard Zumkeller, Mar 18 2012 STATUS approved

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Last modified August 3 07:58 EDT 2021. Contains 346435 sequences. (Running on oeis4.)