

A199969


a(n) = the greatest nondivisor h of n (1<h<n), or 0 if no such h exists.


7



0, 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75
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OFFSET

1,3


COMMENTS

From Paul Curtz, Feb 09 2015: (Start)
The nonnegative numbers with 0 instead of 1. See A254667(n), which is linked to the Bernoulli numbers A164555(n)/A027642(n), an autosequence of the second kind.
Offset 0 could be chosen.
An autosequence of the second kind is a sequence whose main diagonal is the first upper diagonal multiplied by 2. If the first upper diagonal is
s0, s1, s2, s3, s4, s5, ...,
the sequence is
Ssk(n) = 2*s0, s0, s0 + 2*s1, s0 +3*s1, s0 + 4*s1 + 2*s2, s1 + 5*s1 + 5*s2, etc.
The corresponding coefficients are A034807(n), a companion to A011973(n).
The binomial transform of Ssk(n) is (1)^n*Ssk(n).
Difference table of a(n):
0, 0, 2, 3, 4, 5, 6, 7, ...
0, 2, 1, 1, 1, 1, 1, ...
2, 1, 0, 0, 0, 0 ...
3, 1, 0, 0, 0, ...
4, 1, 0, 0, ...
5, 1, 0, ...
6, 1, ...
7, ...
etc.
a(n) is an autosequence of the second kind. See A054977(n).
The corresponding autosequence of the first kind (a companion) is 0, 0 followed by the nonnegative numbers (A001477(n)). Not in the OEIS.
Ssk(n) = 2*Sfk(n+1)  Sfk(n) where Sfk(n) is the corresponding sequence of the first kind (see A254667(n)).
(End)


LINKS

Table of n, a(n) for n=1..76.
Index entries for linear recurrences with constant coefficients, signature (2,1).


FORMULA

a(n) = n1 for n>=3.


MATHEMATICA

Join[{0, 0}, Table[Max[Complement[Range[n], Divisors[n]]], {n, 3, 70}]] (* or *) Join[{0, 0}, Range[2, 70]] (* Harvey P. Dale, May 31 2014 *)


PROG

(PARI) if(n>2, n1, 0) \\ Charles R Greathouse IV, Sep 02 2015


CROSSREFS

Cf. A199968 (the smallest nondivisor h of n (1<h<n)), A199970. A001477, A011973, A034807, A054977, A254667.
Sequence in context: A020725 A119972 A131738 * A303502 A000027 A001477
Adjacent sequences: A199966 A199967 A199968 * A199970 A199971 A199972


KEYWORD

nonn,easy


AUTHOR

Jaroslav Krizek, Nov 26 2011


STATUS

approved



