A120411 If A is a set of integers, the (2-fold) sumset consists of all the numbers which can be written as the sum of two (not necessarily distinct) elements in A. a(n) is the number of subsets of [1,2n] which are sumsets for some set of positive integers.

1, 3, 7, 15, 30, 59, 114, 219, 416, 783, 1461, 2722, 5048, 9341, 17243, 31674, 58037, 105936, 192522, 348832

Offset

1,2

Comments

The relation a(n+1)-a(n) = A190820(n) seems to hold. - Giovanni Resta, Jan 15 2013

Links

Table of n, a(n) for n=1..20.

Example

a(5)=30 because two of the 31 (nonempty) subsets of [1,5], namely {1,2,4,5} and {1,2,3,4,5} have the sumset {2,3,4,5,6,7,8,9,10} and no two other subsets of [1,5] have the same sumset.

Crossrefs

Sequence in context: A182726 A023610 A062544 * A350606 A224520 A291754

Adjacent sequences: A120408 A120409 A120410 * A120412 A120413 A120414

Keyword

nonn,more

Author

David S. Newman, Jul 05 2006

Extensions

a(14)-a(20) from Carl Najafi, Jan 15 2013

Status

approved