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a(n) = nextprime(ceiling(n/2)-1), where nextprime(n) is the smallest prime > n.
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%I #7 Jun 05 2021 14:34:41

%S 2,2,2,2,3,3,5,5,5,5,7,7,7,7,11,11,11,11,11,11,11,11,13,13,13,13,17,

%T 17,17,17,17,17,17,17,19,19,19,19,23,23,23,23,23,23,23,23,29,29,29,29,

%U 29,29,29,29,29,29,29,29,31,31,31,31,37,37,37,37,37,37

%N a(n) = nextprime(ceiling(n/2)-1), where nextprime(n) is the smallest prime > n.

%C For n >= 3, a(n) is the smallest prime appearing among the larger parts of the partitions of n into two parts.

%H <a href="/index/Par#part">Index entries for sequences related to partitions</a>

%F a(n) = A151800(ceiling(n/2)-1).

%F a(n) = A151800(floor((n-1)/2)). - _Wesley Ivan Hurt_, Jun 05 2021

%e a(7) = 5; 7 has three partitions into two parts: (6,1), (5,2) and (4,3). The smallest prime among the larger parts is 5, so a(7) = 5.

%t Table[NextPrime[Ceiling[n/2] - 1, 1], {n, 100}]

%Y Cf. A151800.

%K nonn,easy

%O 1,1

%A _Wesley Ivan Hurt_, May 10 2019