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A024011
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Numbers n such that n-th prime divides sum of first n primes.
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10
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OFFSET
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1,2
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COMMENTS
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No other terms below pi(10^12) = 37607912018. - Jon E. Schoenfield, Sep 11 2008
No other terms below pi(10^14) = 3204941750802. - Giovanni Resta, Jan 09 2014
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LINKS
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Table of n, a(n) for n=1..5.
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EXAMPLE
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The third prime, 5, divides 2 + 3 + 5 = 10, so 3 is in the sequence.
2 + 3 + 5 + 7 = 17, which is not divisible by the fourth prime, 7, so 4 is not in the sequence.
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MATHEMATICA
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s = 0; For[i = 1, i <= 5 * 10^7, i++, s = s + Prime[i]; If[Mod[s, Prime[i + 1]] == 0, Print[i + 1]]]
With[{prs = Prime[Range[221000000]]}, PrimePi /@ Transpose[Select[Thread[{Accumulate[prs], prs}], Divisible[#[[1]], #[[2]]] &]][[2]]] (* Harvey P. Dale, Jul 23 2013 *)
nMax = 50000; primeSums = Accumulate[Prime[Range[nMax]]]; Select[Range[nMax], Divisible[primeSums[[#]], Prime[#]] &] (* Alonso del Arte, Nov 11 2019 *)
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PROG
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(PARI) s=0; t=0; for(w=2, 1000000000, if(isprime(w), s=s+w; t=t+1; if(s%w, print(t)), ))
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CROSSREFS
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Cf. A007506, A028581, A028582, A071089.
Sequence in context: A002857 A203314 A174652 * A229197 A188721 A212996
Adjacent sequences: A024008 A024009 A024010 * A024012 A024013 A024014
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KEYWORD
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nonn,nice,hard,more
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AUTHOR
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G. L. Honaker, Jr.
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EXTENSIONS
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a(5) from Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), May 14 2000
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STATUS
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approved
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