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Search: id:A084833
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| A084833 |
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a(n) is the smallest number such that a(n)+a(n-1), a(n)+a(n-1)+a(n-2), ..., a(n)+...+a(1) are not prime. |
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1
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| 1, 3, 5, 1, 15, 9, 15, 6, 3, 6, 21, 6, 3, 6, 15, 6, 3, 6, 3, 9, 3, 9, 15, 6, 3, 6, 3, 9, 9, 9, 3, 9, 9, 9, 3, 6, 3, 3, 3, 3, 3, 6, 15, 6, 3, 3, 3, 6, 9, 6, 3, 6, 9, 9, 3, 6, 3, 6, 15, 6, 3, 6, 3, 9, 3, 9, 3, 9, 9, 6, 3, 6, 9, 6, 3, 3, 3, 6, 3, 9, 3, 6, 3, 3, 3, 6, 3, 6, 3, 6, 9, 6, 3, 3, 3, 6, 9, 6, 3
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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No sum of a continuous subsequence is ever prime. The sequence consists only of multiples of 3 after n=4?
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EXAMPLE
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a(5)=15 as 1+3+5+1+15=25, 3+5+1+15=24 and 5+1+15=21
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PROGRAM
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(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 }
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CROSSREFS
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Cf. A084834.
Sequence in context: A138259 A077021 A143250 this_sequence A069111 A021288 A140735
Adjacent sequences: A084830 A084831 A084832 this_sequence A084834 A084835 A084836
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KEYWORD
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nonn
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AUTHOR
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Jon Perry (perry(AT)globalnet.co.uk), Jun 06 2003
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