A138797 Least possible T(k) with T(k)-T(j)=n, where T(i)>0 are the triangular numbers A000217.

3, 6, 10, 6, 21, 10, 36, 10, 55, 21, 15, 28, 15, 21, 136, 45, 21, 55, 21, 36, 28, 78, 45, 28, 36, 28, 406, 120, 36, 136, 528, 36, 55, 36, 91, 190, 66, 45, 55, 231, 45, 253, 45, 55, 91, 300, 153, 55, 78, 66, 55, 378, 55, 91, 66, 78, 136, 465, 66, 496, 153, 66, 2080, 66, 171

Offset

2,1

Comments

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

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

Links

Table of n, a(n) for n=2..66.

Example

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

Mathematica

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

Crossrefs

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

Sequence in context: A139762 A055262 A353199 * A333576 A009019 A198467

Adjacent sequences: A138794 A138795 A138796 * A138798 A138799 A138800

Keyword

nonn

Author

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

Status

approved