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 A033998 Numbers n such that the sum of the primes <= n is a square. 4
 23, 22073, 67187, 79427, 10729219, 3531577135439 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS G. L. Honaker Jr. and C. Caldwell, Prime Curios!: 9 G. L. Honaker Jr. and C. Caldwell, Prime Curios!: 3531577135439 C. Riveras, PrimePuzzles.Net, Problem 9: Sum of first k primes is perfect square FORMULA a(n) = Prime(A033997(n)) EXAMPLE 2+3+5+7+11+13+17+19+23 = 10^2 is a square, so 23 is in the sequence. MATHEMATICA Prime[#]&/@Flatten[Position[Accumulate[Prime[Range[710000]]], _?(IntegerQ[ Sqrt[#]]&)]] (* This program will generate the first 5 terms of the sequence. *) (* Harvey P. Dale, Jun 22 2013 *) PROG (PARI) s=0; forprime(p=2, 1e6, if(issquare(s+=p), print1(p", "))) \\ Charles R Greathouse IV, Feb 01 2013 CROSSREFS Cf. A000040, A033997, A061888, A061890. Sequence in context: A028693 A324255 A273940 * A157167 A273192 A233210 Adjacent sequences:  A033995 A033996 A033997 * A033999 A034000 A034001 KEYWORD nonn AUTHOR Calculated by Jud McCranie EXTENSIONS 3531577135439 from Giovanni Resta, May 27 2003 Edited by Ray Chandler, Mar 20 2007 STATUS approved

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Last modified September 29 10:06 EDT 2020. Contains 337428 sequences. (Running on oeis4.)