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A140651 A140579^(-1) * A000290, the squares starting (1, 4, 9, ...). 1
1, 2, 3, 8, 5, 36, 7, 32, 27, 100, 11, 144, 13, 196, 225, 128, 17, 324, 19, 400, 441, 484, 23, 576, 125, 676, 243, 784, 29, 900, 31, 512, 1089, 1156, 1225, 1296, 37, 1444, 1521, 1600, 41, 1764, 43, 1936, 2025, 2116, 47, 2304, 343, 2500, 2601, 2704, 53, 2916, 3025, 3136, 3249, 3364, 59, 3600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For n > 1, a(n) = n iff n is prime.

a(n) is n times the least common multiple of the proper divisors of n, a(n) = n*A048671(n). - Peter Luschny, Jun 22 2011

LINKS

Table of n, a(n) for n=1..60.

FORMULA

A140579^(-1) * (1, 4, 9, 16, 25, ...).

EXAMPLE

A140579 = an infinite lower triangular matrix with A014963 in the main diagonal and the rest zeros; where A014963 = (1, 2, 3, 2, 5, 1, 7, ...).

a(5) = 5 = (1/A014963(5)) * 25 = (1/5)*25.

MAPLE

A140651  := n -> n*ilcm(op(numtheory[divisors](n) minus {1, n})); seq(A140651(i), i=1..60); # Peter Luschny, Jun 22 2011

CROSSREFS

Cf. A140579, A014963.

Sequence in context: A119794 A117987 A091136 * A190997 A184392 A007955

Adjacent sequences:  A140648 A140649 A140650 * A140652 A140653 A140654

KEYWORD

nonn

AUTHOR

Gary W. Adamson and Mats Granvik, May 20 2008

EXTENSIONS

a(15)-a(60) from Peter Luschny, Jun 22 2011

STATUS

approved

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Last modified February 24 18:11 EST 2021. Contains 341577 sequences. (Running on oeis4.)