A120411 - OEIS

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

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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 A373089

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