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 A247278 Least integer k > 0 such that k*n - prime(k) is a square. 3
 1, 1, 4, 29, 1, 3, 4, 43, 3, 1, 5, 37, 2, 5, 9, 19, 1, 267, 22, 23, 4, 3, 43, 57, 2, 1, 46, 19, 20, 5, 4, 23, 440, 3, 5, 162, 1, 7, 20, 499, 2, 74, 4, 128, 29, 9, 927, 215, 156, 1, 96, 91, 7, 1058, 73, 162, 3, 763, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,3 COMMENTS Conjecture: a(n) exists for any n > 1. Note that k*n - prime(k) < 0 if k > e^(n + 1). LINKS Zhi-Wei Sun, Table of n, a(n) for n = 2..10000 Zhi-Wei Sun, A new theorem on the prime-counting function, arXiv:1409.5685, 2014. Zhi-Wei Sun, A new theorem on the prime-counting function, Ramanujan J. 42 (2017), no.1, 59-67. (Cf. Conjecture 4.1.) FORMULA a(A059100(n)) = 1. - Michel Marcus, Sep 28 2014 EXAMPLE a(5) = 29 since 29 * 5 - prime(29) = 145 - 109 = 6^2. MATHEMATICA SQ[n_] := IntegerQ[Sqrt[n]] Do[k = 1; Label[aa]; If[SQ[k * n - Prime[k]], Print[n, " ", k]; Goto[bb]]; k = k + 1; Goto[aa]; Label[bb]; Continue, {n, 2, 60}] CROSSREFS Cf. A000040, A000290, A247893, A247895. Sequence in context: A307553 A327436 A339266 * A278823 A042597 A255635 Adjacent sequences: A247275 A247276 A247277 * A247279 A247280 A247281 KEYWORD nonn AUTHOR Zhi-Wei Sun, Sep 27 2014 STATUS approved

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Last modified February 23 06:40 EST 2024. Contains 370267 sequences. (Running on oeis4.)