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a(1) = 1, a(n) = the smallest composite multiple of n not included earlier such that every partial sum is prime.
1

%I #14 Apr 24 2015 09:22:07

%S 1,4,6,8,10,12,42,24,72,20,132,36,52,14,30,16,68,54,76,80,126,88,92,

%T 168,150,78,108,280,290,210,310,32,198,136,140,144,222,114,234,40,410,

%U 294,172,176,90,138,282,48,784,50,510,156,424,378,440,672,342,58,590,180,366,124,252,320

%N a(1) = 1, a(n) = the smallest composite multiple of n not included earlier such that every partial sum is prime.

%C First 23 terms are the same as in A073669; a(24) = 168 = 7*24 while A073669(24) = 24 = A073669(8). - _Zak Seidov_, Apr 24 2015

%H Charles R Greathouse IV, <a href="/A073670/b073670.txt">Table of n, a(n) for n = 1..10000</a>

%o (PARI) earlier(v,n,k)=for(i=1,n-1,if(v[i]==k, return(k))); 0

%o list(lim)=my(v=vector(lim\1),s,k);s=v[1]=1;for(n=2,#v,k=n; while(isprime(k) || !isprime(s+k) || earlier(v,n,k),k+=n);s+=k;v[n]=k);v \\ _Charles R Greathouse IV_, Apr 24 2015

%Y Cf. A073669.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Aug 11 2002

%E More terms from _Sascha Kurz_, Feb 01 2003

%E Data corrected by _Zak Seidov_, Apr 24 2015

%E More terms from _Charles R Greathouse IV_, Apr 24 2015