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 A205006 a(n) = s(k)-s(j), where (s(k),s(j)) is the least pair of distinct triangular numbers for which n divides their difference. 5
 2, 2, 3, 4, 5, 12, 7, 8, 9, 20, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 56, 29, 30, 31, 32, 33, 34, 35, 72, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 132, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 156, 79, 80, 81 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For a guide to related sequences, see A204892. LINKS Antti Karttunen, Table of n, a(n) for n = 1..23515 MATHEMATICA (See the program at A205002.) PROG (PARI) A205006(n) = for(k=2, oo, my(sk=binomial(k+1, 2)); for(j=1, k-1, if(!((sk-binomial(j+1, 2))%n), return(sk-binomial(j+1, 2))))); \\ Antti Karttunen, Sep 27 2018 CROSSREFS Cf. A000217, A205002, A205007, A204892. Cf. A318894 (gives the positions where a(n) is not n). Sequence in context: A014535 A210642 A263140 * A123560 A060407 A083702 Adjacent sequences:  A205003 A205004 A205005 * A205007 A205008 A205009 KEYWORD nonn AUTHOR Clark Kimberling, Jan 21 2012 EXTENSIONS More terms from Antti Karttunen, Sep 27 2018 STATUS approved

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Last modified July 20 14:12 EDT 2019. Contains 325182 sequences. (Running on oeis4.)