login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A237739 a(0) = 1, a(2n) = nthcomposite(a(n)-1), a(2n+1) = nthprime(a(n)), where nthcomposite = A002808, nthprime = A000040. 5
1, 2, 4, 3, 8, 7, 6, 5, 14, 19, 12, 17, 10, 13, 9, 11, 22, 43, 28, 67, 20, 37, 26, 59, 16, 29, 21, 41, 15, 23, 18, 31, 33, 79, 60, 191, 40, 107, 91, 331, 30, 71, 52, 157, 38, 101, 81, 277, 25, 53, 42, 109, 32, 73, 57, 179, 24, 47, 34, 83, 27, 61, 45, 127, 48 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

A071574(a(n)) = n; a(A071574(n)) = n for n > 0.

LINKS

Reinhard Zumkeller (terms 0-300) & Antti Karttunen, Table of n, a(n) for n = 0..4095

Index entries for sequences that are permutations of the natural numbers

FORMULA

a(0) = 1, a(2n) = nthcomposite(a(n)-1), a(2n+1) = nthprime(a(n)), where nthcomposite = A002808, nthprime = A000040. - Antti Karttunen, Apr 04 2015

PROG

(Haskell)

import Data.List (elemIndex); import Data.Maybe (fromJust)

a237739 = fromIntegral . (+ 1) . fromJust . (`elemIndex` a071574_list)

(PARI)

default(primelimit, (2^31)+(2^30));

A002808(n) = { my(k=-1); while( -n + n += -k + k=primepi(n), ); n }; \\ This function from M. F. Hasler

A237739(n) = if(0==n, 1, if(!(n%2), A002808(A237739(n/2)-1), prime(A237739((n-1)/2))));

for(n=0, 4095, write("b237739.txt", n, " ", A237739(n)));

\\ Antti Karttunen, Apr 04 2015

(Scheme, with memoizing definec-macro)

(definec (A237739 n) (cond ((zero? n) 1) ((odd? n) (A000040 (A237739 (/ (- n 1) 2)))) (else (A002808 (+ -1 (A237739 (/ n 2)))))))

;; Antti Karttunen, Apr 04 2015

CROSSREFS

Inverse: A071574.

Cf. A000040, A002808.

Compare also to the permutation A246378.

Sequence in context: A125566 A255833 A166133 * A337909 A358523 A111699

Adjacent sequences: A237736 A237737 A237738 * A237740 A237741 A237742

KEYWORD

nonn,look

AUTHOR

Reinhard Zumkeller, Apr 30 2014

EXTENSIONS

Name replaced by an explicit recurrence. - Antti Karttunen, Apr 04 2015

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 28 02:51 EST 2022. Contains 358406 sequences. (Running on oeis4.)