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 A264858 Integers k such that A007504(k) + 1 is a square. 1
 0, 17, 539, 652, 6420, 350857847 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Integers k such that the sum of the first k primes + 1 is a square. Integers k such that A014284(k+1) is a square. In A110996, it is commented that a(6) > 250000, if it exists. a(6) > 50000000, if it exists. - Jon E. Schoenfield, Nov 29 2015 LINKS Table of n, a(n) for n=1..6. EXAMPLE a(2) = 17 because A007504(17) + 1 = 440 + 1 = 441 is a square. MATHEMATICA t = Accumulate[Prime@ Range@ 100000]; Prepend[Select[Range@ 7000, IntegerQ@ Sqrt[t[[#]] + 1] &], 0] (* Michael De Vlieger, Nov 29 2015, after Zak Seidov at A007504 *) Join[{0}, Position[Accumulate[Prime[Range[6500]]]+1, _?(IntegerQ[Sqrt[ #]]&)]] // Flatten (* Harvey P. Dale, Feb 12 2018 *) PROG (PARI) lista(nn) = { print1(0, ", "); s = 1; for(k=1, nn, s += prime(k); if(issquare(s), print1(k, ", ")); ); } CROSSREFS Cf. A007504, A014284, A033997, A089228, A110996. Sequence in context: A114063 A214135 A193120 * A112716 A218351 A197395 Adjacent sequences: A264855 A264856 A264857 * A264859 A264860 A264861 KEYWORD nonn,more AUTHOR Altug Alkan, Nov 26 2015 EXTENSIONS a(6) from Jinyuan Wang, Aug 09 2023 STATUS approved

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Last modified June 24 19:44 EDT 2024. Contains 373690 sequences. (Running on oeis4.)