login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A189710 Numbers n such that n'' = n'-1 where n' and n'' are respectively the first and the second arithmetic derivative of n (A003415). 5
2, 3, 5, 7, 9, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 185, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The composite numbers in the sequences are: 9, 185, 341, 377, 437, 9005, 30413, 33953, 41009, 51533, 82673, 92909,....

LINKS

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

EXAMPLE

9' = 6, 9''= 6'= 5, 9" = 9'- 1 -> 9 is in the sequence.

MAPLE

#using Michael B. Porter's code from A003415

der:=n->n*add(op(2, p)/op(1, p), p=ifactors(n)[2])

for i from 1 to n do a:=der(der(i))-der(i)+1; if a=0 then j:=j+1; B[j]:=i; end if od

PROG

(Haskell)

import Data.List (elemIndices)

a189710 n = a189710_list !! (n-1)

a189710_list = elemIndices 0 $

   zipWith (-) (map a003415 a003415_list) (map pred a003415_list)

-- Reinhard Zumkeller, May 09 2011

CROSSREFS

Cf. A003415, A007850, A054377, A189639.

Sequence in context: A132630 A033946 A328232 * A024678 A265384 A039786

Adjacent sequences:  A189707 A189708 A189709 * A189711 A189712 A189713

KEYWORD

nonn

AUTHOR

Giorgio Balzarotti, Apr 25 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 30 05:35 EDT 2020. Contains 334712 sequences. (Running on oeis4.)