A332547 - OEIS

A332547

a(n) = largest odd divisor d < n of n*(n+1)/2.

1, 1, 1, 1, 3, 3, 1, 3, 5, 5, 3, 3, 7, 7, 5, 1, 9, 9, 5, 15, 11, 11, 3, 15, 13, 13, 21, 7, 15, 15, 1, 11, 17, 17, 21, 9, 19, 19, 15, 5, 21, 21, 11, 33, 23, 23, 3, 21, 35, 25, 39, 13, 27, 45, 35, 21, 29, 29, 15, 15, 31, 31, 21, 13, 55, 33, 17, 51, 35, 35

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OFFSET

1,5

COMMENTS

Used by Michael J. Collins in the analysis of A082183 and A082184.

LINKS

Hugo Pfoertner, Table of n, a(n) for n = 1..10000

MATHEMATICA

Join[{1}, Table[Select[Divisors[(n(n+1))/2], OddQ[#]&&#<n&]//Max, {n, 2, 80}]] (* Harvey P. Dale, Jul 16 2024 *)

CROSSREFS

Cf. A000217, A068194 (where a(n)=1), A082183, A082184, A332548, A332549 (where a(n)=3).

Sequence in context: A201873 A317931 A002332 * A302694 A245668 A002102

Adjacent sequences: A332544 A332545 A332546 * A332548 A332549 A332550

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 21 2020

STATUS

approved