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Smallest number k such that prime(n)^k is a sum of 3 consecutive primes.
1

%I #45 May 27 2018 01:38:29

%S 64,57,2,2,107,203,1133,1,2,1

%N Smallest number k such that prime(n)^k is a sum of 3 consecutive primes.

%C a(13) through a(23): { 1, 2, 3, 8, 1, 4, 6, 1, 729, 5, 1 }.

%C a(12) > 5387. a(24) > 3320.

%C Smallest prime p such that p^n is equal to the sum of 3 consecutive primes is given by A122706(n).

%e a(1) does not exist because there is no power of 2 that is a sum of 3 consecutive primes.

%e prime(5)^2 = 11^2 = 121 can be written as 37+41+43, therefore a(5)=2.

%o (PARI) { A123994(n) = my(k,t1,t2,t3,m); k=0; while(1, k++; m=prime(n)^k; t1=precprime(m/3); t2=nextprime(m/3); t3=m-t1-t2; if( ispseudoprime(t3) && ( (t3<t1 && t3==precprime(t1-1)) || (t3>t2 && t3==nextprime(t2+1)) ), return(k)); ); }

%Y Cf. A122706.

%K hard,more,nonn

%O 2,1

%A _Alexander Adamchuk_, Oct 31 2006, Nov 02 2006

%E Corrected by _R. J. Mathar_, Jan 13 2007

%E a(8)-a(11) from _Max Alekseyev_, Apr 24 2010