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A138797 Least possible T(k) with T(k)-T(j)=n, where T(i)>0 are the triangular numbers A000217. 3
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 (list; graph; refs; listen; history; text; internal format)
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: A080817 A139762 A055262 * A009019 A198467 A198456

Adjacent sequences:  A138794 A138795 A138796 * A138798 A138799 A138800

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified October 17 11:47 EDT 2019. Contains 328108 sequences. (Running on oeis4.)