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%I #22 Nov 17 2020 05:40:05
%S 8,24,160,896,22528,106496,2228224,9961472,192937984,15569256448,
%T 66571993088,5085241278464,90159953477632,378231999954944,
%U 6614661952700416,477381560501272576,34011184385901985792
%N a(n) = prime(n)*2^prime(n).
%C A lower bound for the 2-color van der Waerden number A005346(prime(n)); see Berlekamp reference. - _Charles R Greathouse IV_, Jul 13 2008
%H E. R. Berlekamp, <a href="http://dx.doi.org/10.4153/CMB-1968-047-7">A construction for partitions which avoid long arithmetic progressions</a>, Canadian Mathematical Bulletin, Vol. 11, No. 3 (1968), pp. 409-414.
%F Sum_{n>=1} 1/a(n) = A157413. - _Amiram Eldar_, Nov 17 2020
%p seq(ithprime(n)*2^ithprime(n),n=1..20);
%t #*2^#&/@Prime[Range[20]] (* _Harvey P. Dale_, Sep 18 2020 *)
%o (PARI) a(n) = prime(n)*2^prime(n); \\ _Michel Marcus_, May 14 2017
%Y Cf. A005346, A034785, A157413.
%K nonn
%O 1,1
%A _Jorge Coveiro_, Dec 26 2004
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