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A235991 Numbers with an odd arithmetic derivative, cf. A003415. 4
2, 3, 5, 6, 7, 10, 11, 13, 14, 17, 18, 19, 22, 23, 26, 27, 29, 30, 31, 34, 37, 38, 41, 42, 43, 45, 46, 47, 50, 53, 54, 58, 59, 61, 62, 63, 66, 67, 70, 71, 73, 74, 75, 78, 79, 82, 83, 86, 89, 90, 94, 97, 98, 99, 101, 102, 103, 105, 106, 107, 109, 110, 113 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A165560(a(n)) = 1; A003415(a(n)) mod 2 = 1;

A007814(a(n)) <= 1, A006519(a(n)) <= 2.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

n is in this sequence iff either n is congruent to 2 modulo 4 or n and Omega(n) are both odd. - Charlie Neder, Feb 25 2019

PROG

(Haskell)

a235991 n = a235991_list !! (n-1)

a235991_list = filter (odd . a003415) [0..]

CROSSREFS

Cf. A003415, A006519, A007814, A165560, A235992 (complement), A000040 (subsequence).

Sequence in context: A293427 A293430 A087006 * A325362 A325396 A326533

Adjacent sequences:  A235988 A235989 A235990 * A235992 A235993 A235994

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Mar 11 2014

STATUS

approved

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Last modified July 21 02:02 EDT 2019. Contains 325189 sequences. (Running on oeis4.)