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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
OFFSET
1,2
LINKS
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 A371238 A143481
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Mar 22 2002
EXTENSIONS
Corrected and extended by Ray Chandler, Sep 29 2003
STATUS
approved