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 A218049 Smallest k such that the n numbers k^2 + 1, (k+1)^2 + 1, ..., (k+n-1)^2 + 1 are divisible by a square. 0
 7, 117, 5742, 455356, 35952791 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE a(3) = 5742 as 5742^2+1, 5743^2+1 and 5744^2+1 are divisible by squares. 5742^2+1 = 5 * 17 ^ 2 * 22817; 5743^2+1 = 2 * 5 ^ 2 * 701 x 941; 5744^2+1 = 109 ^ 2 * 2777. MATHEMATICA cnt = 0; k = 0; Table[While[cnt < n, k++; If[! SquareFreeQ[k^2+1], cnt++, cnt = 0]]; k - n + 1, {n, 4}] CROSSREFS Cf. A002522, A217798, A218048. Sequence in context: A297308 A077394 A009696 * A097202 A163202 A213112 Adjacent sequences: A218046 A218047 A218048 * A218050 A218051 A218052 KEYWORD nonn,hard AUTHOR Michel Lagneau, Oct 19 2012 EXTENSIONS a(5) from Giovanni Resta, Oct 21 2012 STATUS approved

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Last modified February 2 19:02 EST 2023. Contains 360024 sequences. (Running on oeis4.)