%I A113320
%S A113320 1,1,3,2,6,4,12,4,6,2,12,28,16
%N A113320 Least integers so ascending descending base exponent transforms all prime.
%C A113320 This is the first sequence submitted as a solution to an "ascending descending 
               base exponent transform inverse problem" where the sequence is iteratively 
               defined such that the transform meets a constraint. The sequence 
               is infinite, but it is hard to characterize the asymptotic cost of 
               adding an n-th term. A003101 is the ascending descending base exponent 
               transform of natural numbers A000027. The ascending descending base 
               exponent transform applied to the Fibonacci numbers is A113122; applied 
               to the tribonacci numbers is A113153; applied to the Lucas numbers 
               is A113154.
%F A113320 a(1) = 1. For n>1: a(n) = min {n>0: SUM[from i = 1 to n] (a(i))^(a(n-i+1)) 
               is prime}.
%e A113320 a(1) = 1 by definition.
%e A113320 a(2) = 1 because 1 is the min such that 1^a(2) + a(2)^1 is prime (p=2).
%e A113320 a(3) = 3 because 3 is the min such that 1^a(3) + 1^1 + a(3)^1 is prime 
               (p=5).
%e A113320 a(4) = 2 because 2 is the min such that 1^a(4) + 1^1 + 3^1 + a(4)^1 is 
               prime (p=7).
%e A113320 a(5) = 6 because 6 is the min such that 1^a(5) + 1^2 + 3^3 + 2^1 + a(5)^1 
               is prime (p=37).
%e A113320 a(6) = 4 = min such that 1^a(6) + 1^6 + 3^2 + 2^3 + 6^1 + a(6)^1 is prime 
               (p=29).
%e A113320 a(7) = 12 because 1^12 + 1^4 + 3^6 + 2^2 + 6^3 + 4^1 + 12^1 = 967 is 
               prime.
%e A113320 a(8) = 4 because 1^4 + 1^12 + 3^4 + 2^6 + 6^2 + 4^3 + 12^1 + 4^1 = 263 
               is prime.
%e A113320 a(9) = 6 because 1^6 + 1^4 + 3^12 + 2^4 + 6^6 + 4^2 + 12^3 + 4^1 + 6^1 
               = 579869 is prime.
%e A113320 a(10) = 2 because 1^2 + 1^6 + 3^4 + 2^12 + 6^4 + 4^6 + 12^2 + 4^3 + 6^1 
               + 2^1 = 9787 is prime.
%e A113320 a(11) = 12 because 1^12 + 1^2 + 3^6 + 2^4 + 6^12 + 4^4 + 12^6 + 4^2 + 
               6^3 + 2^1 + 12^1 = 2179769569 is prime.
%e A113320 a(12) = 28 because 1^28 + 1^12 + 3^2 + 2^6 + 6^4 + 4^12 + 12^4 + 4^6 
               + 6^2 + 2^3 + 12^1 + 28^1 = 16803503 is prime.
%e A113320 a(13) = 16 because 1^16 + 1^28 + 3^12 + 2^2 + 6^6 + 4^4 + 12^12 + 4^4 
               + 6^6 + 2^2 + 12^3 + 28^1 + 16^1 = 8916101075303 is prime.
%Y A113320 Cf. A000040, A005408, A113122, A113153, A113154.
%Y A113320 Sequence in context: A094077 A091018 A160795 this_sequence A092401 A116626 
               A162255
%Y A113320 Adjacent sequences: A113317 A113318 A113319 this_sequence A113321 A113322 
               A113323
%K A113320 easy,nonn
%O A113320 1,3
%A A113320 Jonathan Vos Post (jvospost3(AT)gmail.com), Jan 07 2006