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 A069553 Define S(k) to be the sequence of divisors and multiples of k, e.g. S(1) = 1,2,3,4,5... S(2) = 1,2,4,6,8,10,... S(10) = 1,2,5,10,20,30,40,50,...; a(n) = n-th term of the n-th sequence S(n). 1
 1, 2, 6, 8, 20, 18, 42, 40, 63, 70, 110, 84, 156, 154, 180, 192, 272, 234, 342, 300, 378, 418, 506, 408, 575, 598, 648, 644, 812, 690, 930, 864, 990, 1054, 1120, 1008, 1332, 1330, 1404, 1320, 1640, 1470, 1806, 1716, 1800, 1978, 2162, 1872, 2303, 2250, 2448 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Ivan Neretin, Table of n, a(n) for n = 1..10000 FORMULA a(n) = n*{n - d(n) + 1} where d(n) = number of divisors of n. MATHEMATICA Table[n (n + 1 - DivisorSigma[0, n]), {n, 1, 51}] (* Ivan Neretin, May 25 2015 *) PROG (PARI) a(n) =  n*(n - numdiv(n) + 1); \\ Michel Marcus, Sep 17 2013 CROSSREFS Sequence in context: A140965 A002618 A135616 * A275826 A143481 A093968 Adjacent sequences:  A069550 A069551 A069552 * A069554 A069555 A069556 KEYWORD nonn AUTHOR Amarnath Murthy, Mar 22 2002 EXTENSIONS Corrected and extended by Ray Chandler, Sep 29 2003 STATUS approved

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Last modified September 25 06:32 EDT 2020. Contains 337335 sequences. (Running on oeis4.)