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A133564 a(1)=1. a(n+1) = sum{k=isolated divisors of n} a(k). An isolated divisor, k, of n is a positive divisor of n where neither (k-1) nor (k+1) divides n. 1
1, 1, 0, 1, 1, 2, 2, 3, 4, 5, 6, 7, 9, 10, 12, 14, 18, 19, 25, 26, 31, 34, 40, 41, 53, 55, 64, 69, 82, 83, 100, 101, 119, 126, 144, 148, 180, 181, 206, 216, 250, 251, 292, 293, 334, 352, 392, 393, 460, 463, 522, 541, 606, 607, 696, 704, 784, 810, 892, 893, 1026, 1027, 1127 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,6
LINKS
EXAMPLE
The positive divisors of 20 are 1,2,4,5,10,20. Of these, 1 and 2 are adjacent and 4 and 5 are adjacent. So the isolated divisors of 20 are 10 and 20. Therefore a(21) = a(10) + a(20) = 5 + 26 = 31.
CROSSREFS
Cf. A133565.
Sequence in context: A011873 A173151 A008673 * A342558 A017863 A242634
KEYWORD
nonn
AUTHOR
Leroy Quet, Sep 16 2007
EXTENSIONS
Extended by Ray Chandler, Jun 25 2008
STATUS
approved

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Last modified March 29 02:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)