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A025523 a(n) = 1 + Sum_{ k < n and k | n} a(k). 3
1, 2, 3, 5, 6, 9, 10, 14, 16, 19, 20, 28, 29, 32, 35, 43, 44, 52, 53, 61, 64, 67, 68, 88, 90, 93, 97, 105, 106, 119, 120, 136, 139, 142, 145, 171, 172, 175, 178, 198, 199, 212, 213, 221, 229, 232, 233, 281, 283, 291, 294, 302, 303, 323, 326, 346, 349, 352, 353, 397, 398, 401 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Permanent of n X n (0,1) matrix defined by A(i,j)=1 iff j=1 or i divides j. - Vladeta Jovovic, Jul 05 2003

Partial sums of A074206, ordered factorizations. - Augustine O. Munagi, Jul 10 2007

The subsequence of primes begins: 2, 3, 5, 19, 29, 43, 53, 61, 67, 97, 139, 199, 229, 233, 281, 283, 349, 353, 397, 401. - Jonathan Vos Post

LINKS

Table of n, a(n) for n=1..62.

Herbert S. Wilf, The Redheffer matrix of a partially ordered set, The Electronic Journal of Combinatorics, Volume 11(2), 2004, R#10.

FORMULA

Running sum of A002033.

a(n) = 1 + Sum_{k = 2 to n} a([n/k]) [From Mitchell Lee (worthawholephan(AT)gmail.com), Jul 26 2010]

CROSSREFS

Cf. A002321.

Cf. A074206, A002033.

A173382 is an essentially identical sequence.

Sequence in context: A117142 A238617 A076061 * A173382 A128689 A116137

Adjacent sequences:  A025520 A025521 A025522 * A025524 A025525 A025526

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified September 17 13:00 EDT 2019. Contains 327131 sequences. (Running on oeis4.)