A138797 - OEIS

%I #1 Jun 29 2008 03:00:00

%S 3,6,10,6,21,10,36,10,55,21,15,28,15,21,136,45,21,55,21,36,28,78,45,

%T 28,36,28,406,120,36,136,528,36,55,36,91,190,66,45,55,231,45,253,45,

%U 55,91,300,153,55,78,66,55,378,55,91,66,78,136,465,66,496,153,66,2080,66,171

%N Least possible T(k) with T(k)-T(j)=n, where T(i)>0 are the triangular numbers A000217.

%C For k see A138796, for j see A138798 and for T(j) see A138799.

%C The number of ways n can be written as difference of two triangular numbers is sequence A136107

%e a(4)=10 because T(A138796(4))=10.

%t T=#(#+1)/2&;T[Min[k/.{ToRules[Reduce[{T[k]-T[j]\[Equal]#,0<j<k},{j,k},Integers]]}]]&/@Range[2,100]

%Y Cf. A000217, A109814, A118235, A136107, A138796, A138798, A138799.

%K nonn

%O 2,1

%A Peter Pein (petsie(AT)dordos.net), Mar 30, 2008