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Triangle read by rows in which the n-th row begins with n and contains tau(n) numbers. The r-th term from right is the largest number < n with r divisors, for 1<= r <= tau(n).
1

%I #8 Sep 29 2024 21:10:22

%S 1,2,1,3,1,4,3,1,5,1,6,4,5,1,7,1,8,4,7,1,9,7,1,10,9,7,1,11,1,12,10,9,

%T 11,1,13,1,14,9,13,1,15,9,13,1,16,15,9,13,1,17,1,18,16,15,9,17,1,19,1,

%U 20,16,15,9,19,1,21,9,19,1,22,9,19,1,23,1,24,20,16,22,9,23,1,25,23,1,26,25

%N Triangle read by rows in which the n-th row begins with n and contains tau(n) numbers. The r-th term from right is the largest number < n with r divisors, for 1<= r <= tau(n).

%C The number of terms in the n-th row = tau(n).

%e 1

%e 2 1

%e 3 1

%e 4 3 1

%e 5 1

%e 6 4 5 1

%e 7 1

%e 8 4 7 1

%e 9 7 1

%e ...

%o (PARI) print(1,",");for(i=2,50,v=[1];for(j=2,sigma(i,0),forstep(k=i,1,-1,if(sigma(k,0)==j,v=concat(v,k);break)));forstep(l=length(v),1,-1,print1(v[l],","));print()) \\ Lambert Herrgesell (zero815(AT)googlemail.com), Mar 13 2006

%Y Cf. A079787.

%K nonn,tabf

%O 1,2

%A _Amarnath Murthy_, Feb 03 2003

%E More terms from Lambert Herrgesell (zero815(AT)googlemail.com), Mar 13 2006

%E Offset corrected by _Andrew Howroyd_, Sep 29 2024