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 A242920 Numbers N with prime factors p_1, ... p_n, such that 1/p_1 + sum{i=2..n} p_(i-1)/p_i + p_n/N - (n+2)/N = 1. 1
 6, 10, 14, 15, 22, 26, 34, 35, 38, 46, 58, 62, 74, 82, 86, 94, 106, 118, 122, 134, 142, 143, 146, 158, 166, 178, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 323, 326, 334, 346, 358, 362, 382, 386, 394, 398, 422, 446, 454, 458, 466, 478 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Steve Humble, Create your own mathematical mysteries, +plus magazine, University of Cambridge. EXAMPLE 6=2*3 and 1/2 + 2/3 + 3/6 - 4/6 = 1, so 6 belongs to the sequence. PROG (PARI) isok(n) = f = factor(n)[, 1]; 1/f[1] + sum(i=2, #f, f[i-1]/f[i]) + f[#f]/n - (#f~ + 2)/n == 1; CROSSREFS Sequence in context: A072901 A162409 A226494 * A183072 A225704 A228301 Adjacent sequences:  A242917 A242918 A242919 * A242921 A242922 A242923 KEYWORD nonn AUTHOR Michel Marcus, May 26 2014 STATUS approved

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Last modified August 9 23:26 EDT 2020. Contains 336335 sequences. (Running on oeis4.)