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A210208 Triangle read by rows in which row n lists the divisors of n that are prime powers, A000961. 9

%I

%S 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,

%T 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,

%U 2,3,4,8,1,5,25,1,2,13,1,3,9,27,1,2,4,7

%N Triangle read by rows in which row n lists the divisors of n that are prime powers, A000961.

%C A073093(n) = length of n-th row;

%C A023888(n) = sum of n-th row;

%C A183091(n) = product of n-th row;

%C A034699(n) = T(n,A073093(n)) = maximum of n-th row;

%C {T(n,k):k=1..A073093(n)} subset of {A027750(n,k):k=1..A000005(n)} for all n.

%H Reinhard Zumkeller, <a href="/A210208/b210208.txt">Rows n=1..5000 of triangle, flattened</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Divisor.html">Divisor</a>

%e 1;

%e 1, 2;

%e 1, 3;

%e 1, 2, 4;

%e 1, 5;

%e 1, 2, 3;

%e 1, 7;

%e 1, 2, 4, 8;

%e 1, 3, 9;

%e 1, 2, 5;

%e 1, 11;

%e 1, 2, 3, 4; - _Geoffrey Critzer_, Feb 08 2015

%t Table[Prepend[Select[Divisors[n], PrimeNu[#] == 1 &], 1], {n, 1, 10}]//Grid (* _Geoffrey Critzer_, Feb 08 2015 *)

%o (Haskell)

%o a210208 n k = a210208_tabf !! (n-1) !! (n-1)

%o a210208_row n = a210208_tabf !! (n-1)

%o a210208_tabf = map (filter ((== 1) . a010055)) a027750_tabf

%Y Cf. A010055, A141809.

%K nonn,tabf

%O 1,3

%A _Reinhard Zumkeller_, Mar 18 2012

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Last modified August 14 19:09 EDT 2020. Contains 336483 sequences. (Running on oeis4.)