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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 February 21 10:49 EST 2019. Contains 320372 sequences. (Running on oeis4.)