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Array read by antidiagonals: row n contains the positive integers each with exactly n positive "isolated divisors". A divisor, k, of n is isolated if neither (k-1) nor (k+1) divides n.
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%I #11 Dec 08 2016 09:02:46

%S 3,9,5,15,16,7,36,21,18,8,45,54,24,25,10,126,48,64,27,30,11,96,150,60,

%T 66,28,42,12,144,105,162,63,78,32,49,13,120,168,108,196,70,81,33,121,

%U 14,324,180,198,135,256,72,90,35,169,17,240,378,192,225,140,294,75,100,39

%N Array read by antidiagonals: row n contains the positive integers each with exactly n positive "isolated divisors". A divisor, k, of n is isolated if neither (k-1) nor (k+1) divides n.

%C The left column (column 1) of the array is sequence A133997. The array starts at column 1 and row 2. The only positive integers each with exactly 1 isolated divisor are 1,4,6.

%e 2 isolated divisors: 3, 5, 7, 8, 10, ...

%e 3 isolated divisors: 9, 16, 18, 25, ...

%e 4 isolated divisors: 15, 21, 24, ...

%e etc.

%Y Cf. A133997, A134000.

%K nonn,tabl

%O 2,1

%A _Leroy Quet_, Oct 01 2007

%E Extended by _Ray Chandler_, Jun 25 2008