OFFSET
1,2
COMMENTS
No sum of a continuous subsequence is ever prime. Does the sequence consist only of multiples of 3 after a(4)?
EXAMPLE
a(5) = 15 as 1+3+5+1+15 = 25 is composite, 3+5+1+15 = 24 is composite, 5+1+15 = 21 is composite, and 1+15 = 16 is composite, and no smaller number has this property.
PROG
(PARI) { checkprime(a, b)=local(fl); fl=0; for (i=1, b-1, if (isprime(a+s[i]), fl=1; break)); fl }
{ p=vector(100); p[1]=1; pc=2; while (pc<100, x=1; s=vector(100); for (i=1, pc-1, s[i]=sum(k=i, pc-1, p[k])); i=1; while (checkprime(x, pc), x++); p[pc]=x; pc++); p }
CROSSREFS
KEYWORD
nonn
AUTHOR
Jon Perry, Jun 06 2003
STATUS
approved