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 A074155 Group the natural numbers so that the product of members of a group is a multiple of the sum: (1),(2,3,4,5,6),(7,8,9),(10,11,12),(13,14,15),(16,17,18),(19,20,21),(22,23,24),.... This is the sequence of the ratio of product /sum. 0

%I

%S 1,36,21,40,65,96,133,176,225,280,341,408,481,560,645,736,833,936,

%T 1045,1160,1281,1408,1541,1680,1825,1976,2133,2296,2465,2640,2821,

%U 3008,3201,3400,3605,3816,4033,4256,4485,4720,4961,5208,5461,5720,5985,6256,6533

%N Group the natural numbers so that the product of members of a group is a multiple of the sum: (1),(2,3,4,5,6),(7,8,9),(10,11,12),(13,14,15),(16,17,18),(19,20,21),(22,23,24),.... This is the sequence of the ratio of product /sum.

%C a(n+1) = (3n+1)(n+1) for n >=2.

%F For n>2, a(n) = n(3n-2) = A000567(n).

%p 1,36,seq((3*n+1)*(n+1),n=2..120);

%t Join[{1,36},Table[(3n+1)(n+1),{n,2,50}]] (* _Harvey P. Dale_, Sep 04 2019 *)

%K nonn

%O 1,2

%A _Amarnath Murthy_, Aug 29 2002

%E More terms from _Sascha Kurz_, Jan 15 2003

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Last modified May 28 09:09 EDT 2022. Contains 354112 sequences. (Running on oeis4.)