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A036434 Integers which cannot be written as k+tau(k) for some k. 2
1, 3, 6, 8, 11, 16, 17, 20, 22, 23, 27, 29, 35, 36, 40, 41, 44, 46, 47, 53, 54, 57, 60, 65, 67, 68, 70, 76, 77, 79, 80, 83, 87, 88, 92, 93, 94, 100, 101, 106, 107, 114, 116, 117, 121, 125, 128, 131, 132, 134, 135, 140, 142, 148, 155, 156, 157, 158, 161, 164, 166 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Invented by the HR concept formation program.

LINKS

Table of n, a(n) for n=1..61.

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

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

EXAMPLE

None of 1,2,3,4,5,6,7 are such that k+tau(k)=8, so 8 is in the sequence.

PROG

(PARI) isok(n) = sum(k=1, n, k+numdiv(k) != n) == n; \\ Michel Marcus, Dec 08 2014

CROSSREFS

Cf. A036438.

Sequence in context: A164910 A276583 A135736 * A140400 A190430 A188018

Adjacent sequences:  A036431 A036432 A036433 * A036435 A036436 A036437

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified December 5 21:40 EST 2016. Contains 278771 sequences.