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A036907 Square refactorable numbers. 3
1, 9, 36, 225, 441, 625, 1089, 1521, 2025, 2601, 3249, 3600, 4761, 5625, 6561, 7569, 8100, 8649, 10000, 12321, 15129, 16641, 19881, 22500, 25281, 26244, 28224, 31329, 32400, 33489, 35721, 40401, 45369, 47961, 50625, 56169, 62001, 71289, 84681 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..39.

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

S. Colton, HR - Automatic Theory Formation in Pure Mathematics

EXAMPLE

9 is refactorable because tau(9)=3 and 3 divides 9 and 9 is a square number.

PROG

(PARI) isok(n) = issquare(n) && ! (n % numdiv(n)); \\ Michel Marcus, Aug 31 2013

CROSSREFS

A033950.

Sequence in context: A094973 A038780 A073984 * A027381 A024120 A262782

Adjacent sequences:  A036904 A036905 A036906 * A036908 A036909 A036910

KEYWORD

nonn

AUTHOR

Simon Colton (simonco(AT)cs.york.ac.uk)

STATUS

approved

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Last modified May 26 02:35 EDT 2019. Contains 323579 sequences. (Running on oeis4.)