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Rectangular array read by antidiagonals: a(n, d) is the smallest number that starts an arithmetic progression with common difference d of n numbers with the same number of divisors.
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%I #7 Jun 16 2013 10:38:34

%S 1,2,1,33,3,1,242,3,2,1,11605,213,119,3,1,28374,213,3445,3,2,1,171893,

%T 1383,15026,111,77,5,1,1043710445721,3091,74783,201,8718,5,8,1

%N Rectangular array read by antidiagonals: a(n, d) is the smallest number that starts an arithmetic progression with common difference d of n numbers with the same number of divisors.

%C First two columns are A006558 and A113466. First four rows are A000012, A065559, A113467 and A113468. a(9, 1) is unknown; the rest of the 9th antidiagonal is 8129,88015,201,8718,5,8,3,1.

%e a(4, 3) = 3445 because 3445, 3448, 3451 and 3454 each have 8 divisors.

%Y Cf. A006558, A065559, A113456, A113466, A113467, A113468.

%K nonn,tabl,less

%O 1,2

%A _David Wasserman_, Jan 08 2006