login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

a(1) = 1; for n > 1, a(n) is the smallest even number not already in the sequence such that a(1) + ... + a(n) is a prime.
9

%I #33 Jun 13 2021 09:01:46

%S 1,2,4,6,10,8,12,16,14,24,30,22,18,26,34,36,20,28,38,40,32,42,46,48,

%T 44,52,56,60,54,58,66,50,64,62,70,84,90,72,92,76,86,94,74,88,68,82,80,

%U 102,96,100,114,98,78,112,120,110,108,106,126,122,130,132,134,124,128,118

%N a(1) = 1; for n > 1, a(n) is the smallest even number not already in the sequence such that a(1) + ... + a(n) is a prime.

%C Essentially the same as A054408. - _R. J. Mathar_, Dec 15 2008

%C Conjecture: Every even number appears. - _N. J. A. Sloane_, May 29 2017

%H Chai Wah Wu, <a href="/A073659/b073659.txt">Table of n, a(n) for n = 1..10000</a> (terms n = 1..4097 from N. J. A. Sloane).

%t t = {1}; Do[i = 2; While[! PrimeQ[Total[t] + i] || MemberQ[t, i], i += 2]; AppendTo[t, i], {65}]; t (* _Jayanta Basu_, Jul 04 2013 *)

%o (PARI) v=[1];n=1;while(n<200,if(isprime(n+vecsum(v))&&!vecsearch(vecsort(v),n),v=concat(v,n);n=0);n++);v \\ _Derek Orr_, Jun 01 2015

%Y Cf. A054408, A073660.

%Y See A055265 for a version where the sums of two adjacent terms are primes.

%K nonn,easy

%O 1,2

%A _Amarnath Murthy_, Aug 10 2002

%E More terms from _Sascha Kurz_, Jan 28 2003

%E Offset corrected by _Chai Wah Wu_, Aug 27 2017