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a(n) = A020639(A053790(n)).
2

%I #12 Jan 29 2018 21:13:02

%S 2,2,2,7,2,3,2,2,2,3,2,3,2,3,2,7,2,3,2,3,2,3,2,3,2,3,2,3,2,3,2,41,2,3,

%T 2,3,2,3,2,3,2,59,2,7,2,3,2,3,2,7,2,37,2,2,5,2,2,89,2,3,2,3,2,7,2,3,2,

%U 3,2,3,2,3,2,3,2,3,2,3,2,3,2,3,2,13,2,109,2,2,17,2,2,2,7,2,7,2,2,7,2

%N a(n) = A020639(A053790(n)).

%H Robert Israel, <a href="/A053789/b053789.txt">Table of n, a(n) for n = 1..10000</a>

%e a(4) = 7 because the sum of the first 8 primes is 77 and 7 is its least prime divisor.

%p N:= 2000: # to use primes <= N

%p P:= select(isprime, [2, seq(i, i=3..N, 2)]):

%p A053790:= remove(isprime, ListTools:-PartialSums(P)):

%p map(t -> min(numtheory:-factorset(t)), A053790); # _Robert Israel_, Jan 29 2018

%Y Cf. A013918, A053790, A020639.

%K easy,nonn

%O 1,1

%A _Enoch Haga_, Mar 27 2000

%E Edited by _N. J. A. Sloane_, Mar 16 2008, following explication by _R. J. Mathar_, Feb 26 2008