A140651 A140579^(-1) * A000290, the squares starting (1, 4, 9, ...).

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

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: A117987 A376016 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