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 A066451 a(n) is the number of integers k > 0 such that (n*k+1)/(k^2+1) is an integer. 2
 1, 1, 2, 1, 2, 1, 3, 1, 2, 1, 2, 2, 3, 1, 2, 1, 3, 1, 2, 1, 3, 2, 3, 1, 2, 1, 3, 1, 2, 1, 3, 2, 3, 1, 2, 1, 3, 2, 2, 1, 2, 2, 4, 1, 2, 1, 3, 1, 2, 1, 2, 2, 3, 1, 3, 1, 5, 1, 2, 1, 2, 2, 3, 1, 2, 1, 3, 1, 2, 1, 2, 3, 4, 1, 2, 1, 3, 1, 2, 2, 2, 2, 4, 1, 2, 1, 3, 1, 3, 1, 3, 2, 3, 1, 2, 1, 3, 1, 2, 1, 2, 2, 3, 1, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Table of n, a(n) for n=1..105. EXAMPLE a(57)=5 because (57*k+1)/(k^2+1) is an integer for k = 1,2,5,7,57. PROG (PARI) a(n) = sum(k=1, n, denominator((n*k+1)/(k^2+1)) == 1); \\ Michel Marcus, Feb 17 2021 CROSSREFS Sequence in context: A195155 A178544 A161506 * A328048 A363522 A091090 Adjacent sequences: A066448 A066449 A066450 * A066452 A066453 A066454 KEYWORD nonn AUTHOR Benoit Cloitre, Dec 29 2001 STATUS approved

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Last modified November 28 17:53 EST 2023. Contains 367419 sequences. (Running on oeis4.)