A085761 Number of triangular numbers between n and 2n (inclusive).

1, 1, 2, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 3, 3, 2, 2, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 4, 3, 3, 3, 3, 4, 4, 4, 4, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7

Offset

1,3

Links

Table of n, a(n) for n=1..105.

Mathematica

With[{trnos=Accumulate[Range[100]]}, Table[Count[trnos, _?(n<=#<=2n&)], {n, 110}]] (* Harvey P. Dale, Jul 23 2013 *)

Crossrefs

Sequence in context: A118916 A107800 A245760 * A352884 A102382 A024890

Adjacent sequences: A085758 A085759 A085760 * A085762 A085763 A085764

Keyword

easy,nonn

Author

Amarnath Murthy, Jason Earls, Jul 22 2003

Status

approved