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A189481 Numbers n such that x' = n has a unique solution, where x' denotes the arithmetic derivative (A003415). 5
4, 5, 6, 7, 8, 9, 13, 15, 19, 25, 27, 33, 41, 43, 49, 51, 59, 63, 69, 73, 77, 85, 95, 99, 105, 109, 113, 115, 121, 133, 135, 139, 141, 143, 153, 155, 159, 161, 169, 171, 175, 181, 187, 193, 201, 203, 225, 227, 229, 235, 239, 249, 251, 253, 259, 265, 267, 273 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The unique solutions are in A189482. Ufnarovski and Ahlander list these numbers on page 7 of their paper.

Interestingly, for about half the numbers n in this sequence, the unique solution is x = 2(n-2) because n-2 is prime.

REFERENCES

See A003415.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..5000

Victor Ufnarovski and Bo Ahlander, How to Differentiate a Number, J. Integer Seqs., Vol. 6, 2003.

FORMULA

n such that A099302(n) = 1.

CROSSREFS

Cf. A003415, A099302, A189482.

Sequence in context: A285623 A213518 A214419 * A123977 A109602 A084991

Adjacent sequences:  A189478 A189479 A189480 * A189482 A189483 A189484

KEYWORD

nonn

AUTHOR

T. D. Noe, Apr 22 2011

STATUS

approved

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Last modified October 25 21:15 EDT 2021. Contains 348256 sequences. (Running on oeis4.)