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A282519 Refactorable numbers that are the sum of two refactorable numbers in exactly one way. 1
2, 9, 18, 24, 60, 88, 625, 1089, 2601, 1500625 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Sequence is a result of investigation on the marked region in graph of A172398(A033950(n)) that is in Links section. Also there are other sequences that marked region has.

LINKS

Table of n, a(n) for n=1..10.

Altug Alkan, Illustration of A172398(A033950(n))

S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999.

Joshua Zelinsky, Tau Numbers: A Partial Proof of a Conjecture and Other Results , Journal of Integer Sequences, Vol. 5 (2002), Article 02.2.8

EXAMPLE

Refactorable number 1500625 is a term because 1500625 is the sum of two refactorable numbers in exactly one way, that is, 1500625 = 5^4 * 7^4 = 3^2 * 131^2 + 2^7 * 13 * 809.

CROSSREFS

Cf. A033950, A172398, A280634, A281663.

Sequence in context: A126082 A083707 A240651 * A103256 A028881 A294535

Adjacent sequences:  A282516 A282517 A282518 * A282520 A282521 A282522

KEYWORD

nonn,more

AUTHOR

Altug Alkan, Feb 17 2017

EXTENSIONS

a(10) from Giovanni Resta, Feb 17 2017

STATUS

approved

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Last modified January 24 16:34 EST 2020. Contains 331207 sequences. (Running on oeis4.)