A177732 The sums of two or more consecutive positive numbers, the largest being even.

3, 7, 9, 10, 11, 15, 18, 19, 20, 21, 23, 26, 27, 30, 31, 33, 34, 35, 36, 39, 40, 42, 43, 45, 47, 49, 50, 51, 52, 54, 55, 57, 58, 59, 60, 63, 66, 67, 68, 69, 70, 71, 72, 74, 75, 77, 78, 79, 80, 81, 82, 83, 84, 87, 90, 91, 93, 95, 98, 99, 100, 102, 103, 104, 105, 106, 107, 108

Offset

1,1

Comments

Numbers of the form (j+2l)*(2l-j+1)/2 with j>=1 and 2l>j. Subsequences are A014105 where >=3, (j=1), A014107 where >=9 (j=2). - R. J. Mathar, Jul 14 2012

Links

Table of n, a(n) for n=1..68.

Example

3=1+2, 7=3+4, 9=2+3+4, 10=1+2+3+4, 11=5+6,..

Mathematica

z=200; lst2={}; Do[c=a; Do[c+=b; If[c<=2*z, AppendTo[lst2, c]], {b, a-1, 1, -1}], {a, 2, z, 2}]; Union@lst2
With[{upto=108}, Select[Union[Flatten[Table[Accumulate[Range[2n-1, 1, -1]]+ 2n, {n, upto/4}]]], #<=upto&]] (* Harvey P. Dale, May 19 2019 *)

Crossrefs

Cf. A177712, A177713, A177731.

Sequence in context: A194407 A241662 A097475 * A081339 A063551 A160800

Adjacent sequences: A177729 A177730 A177731 * A177733 A177734 A177735

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, May 12 2010

Status

approved