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A033997
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Numbers n such that sum of first n primes is a square.
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3
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OFFSET
| 1,1
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LINKS
| G. L. Honaker Jr. and C. Caldwell, Prime Curios!: 9
C. Riveras, PrimePuzzles.Net, Problem 9: Sum of first k primes is perfect square
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FORMULA
| a(n) = PrimePi(A033998(n)).
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EXAMPLE
| Sum of first 9 primes is 2+3+5+7+11+13+17+19+23 = 100, which is square, so 9 is in the sequence.
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MATHEMATICA
| p = 2; s = 0; lst = {}; While[p < 10^7, s = s + p; If[ IntegerQ@ Sqrt@ s, AppendTo[lst, PrimePi@ p]; Print@ lst]; p = NextPrime@ p] (* Zak Seidov, Apr 11 2011 *)
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CROSSREFS
| Cf. A000040, A033998, A061888, A061890 (associated squares).
Sequence in context: A013827 A058428 A069704 * A068729 A159775 A203744
Adjacent sequences: A033994 A033995 A033996 * A033998 A033999 A034000
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KEYWORD
| nonn
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AUTHOR
| Calculated by Jud McCranie (JudMcCranie(AT)ugaalum.uga.edu)
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EXTENSIONS
| 126789311423 from Giovanni Resta (g.resta(AT)iit.cnr.it), May 27 2003
Edited by Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 20 2007
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