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A139218 Smallest positive integer of the form 3k+2 such that all subsets of {a(1),...,a(n)} have a different sum. 3
2, 5, 8, 14, 23, 41, 92, 179, 353, 716, 1427, 2849, 5708, 11411 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

COMMENTS

(1) It appears that {a(n+1)-2a(n)} is eventually periodic, with values {1,-2,-2,-5,-5,10,-5,-5,10,-5,-5,10,-5,...}.

(2) See A139217 for the corresponding sequence using integers of the form 3k+1.

(3) Maximilian Hasler, in a SeqFan memo dated Apr. 9, 2008, notes that the Jacobsthal sequence (A001045) from a(2) on (i.e., 1,3,5,11,21,...) gives the smallest positive odd integer such that all subsets of {a(2),...,a(n)} have a different sum.

FORMULA

It appears that a(n)=a(n-1)+a(n-2)+2a(n-3), for n>6.

CROSSREFS

Cf. A001045, A139217.

Sequence in context: A000094 A058578 A023674 * A017988 A103077 A090980

Adjacent sequences:  A139215 A139216 A139217 * A139219 A139220 A139221

KEYWORD

nonn

AUTHOR

John W. Layman (layman(AT)math.vt.edu), Apr 11 2008

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Last modified February 15 07:19 EST 2012. Contains 205703 sequences.