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 A123173 Least semiprime s for which the Mertens function M(s) = n. 0
 33, 9, 4, 39, 94, 95, 218, 219, 221, 554, 586, 1357, 1389, 1393, 1403, 1405, 1418, 3227, 3233, 3235, 3239, 3241, 3242, 3277, 3281, 3293, 3295, 8201, 8413, 8486, 8489, 8495, 8491, 8503, 8506, 8507, 8509, 8519, 8511, 11759, 11761, 11762, 11769, 11785, 11771 (list; graph; refs; listen; history; text; internal format)
 OFFSET -3,1 LINKS FORMULA a(n) = min{s in A001358 and A002321(s) = n}. EXAMPLE a(-3) = 33 = 3 * 11 = the first semiprime s for which the Mertens function M(s) = -3. a(-2) = 9 = 3^2 = the first semiprime s for which the Mertens function M(s) = -2. a(-1) = 4 = 2^2 = the first semiprime s for which the Mertens function M(s) = -1. a(0) = 39 = 3 * 13 = min{A001358 INTERSECTION A028442} = the first semiprime s for which the Mertens function M(s) = 0. a(1) = 94 = 2 * 47 = min{A001358 INTERSECTION A118684} = the first semiprime s for which the Mertens function M(s) = 1. a(2) = 95 = 5 * 19 = the first semiprime s for which the Mertens function M(s) = 2. a(3) = 341 = 11 * 31 = the first semiprime s for which the Mertens function M(s) = 3. PROG (PARI) nextsemip(n) = {x = n; while (bigomega(x) != 2, x++); x; } a(n) = {sp = 4; while (mertens(sp) != n, sp = nextsemip(sp+1)); sp; } \\ Michel Marcus, Sep 24 2013 CROSSREFS Cf. A001358, A002321, A028442, A118684. Sequence in context: A113458 A120584 A236177 * A147021 A200897 A138839 Adjacent sequences:  A123170 A123171 A123172 * A123174 A123175 A123176 KEYWORD easy,nonn AUTHOR Jonathan Vos Post, Oct 02 2006 EXTENSIONS a(3) corrected and a(4)-a(41) added by Michel Marcus, Sep 24 2013 STATUS approved

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Last modified April 9 10:52 EDT 2020. Contains 333348 sequences. (Running on oeis4.)