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A128688 a(1)=1. For n>1, a(n) is the smallest even number such that every subset of a(1), ..., a(n) adds to a nonprime. 3
1, 8, 24, 86, 90, 780, 5940, 52350, 278460, 40768260, 6847205430, 5027286840810 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The first 7 terms are from Rivera's puzzle 84.

The sequences is infinite [Chris Nash]. - N. J. A. Sloane, Jan 20 2017

LINKS

Table of n, a(n) for n=1..12.

Chris Nash, Proof that A052349, A128687, and A128688 are infinite [Cached copy of proof, from The Prime Puzzles and Problems website]

Carlos Rivera, Puzzle 84

CROSSREFS

Cf. A052349 (no restrictions on even or odd), A128687 (restricted to odd numbers).

Sequence in context: A296400 A297808 A097544 * A279162 A217016 A019260

Adjacent sequences:  A128685 A128686 A128687 * A128689 A128690 A128691

KEYWORD

hard,nonn

AUTHOR

T. D. Noe, Mar 20 2007

EXTENSIONS

a(11) from Donovan Johnson, Apr 18 2010

a(12) from Donovan Johnson, Jul 06 2010

STATUS

approved

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Last modified September 22 05:47 EDT 2019. Contains 327287 sequences. (Running on oeis4.)