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

 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 60th year, we have over 367,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A284584 a(1) = 0; for n > 1, if n is not squarefree, then a(n) = A057627(n), otherwise a(n) = A013928(n). 3
 0, 1, 2, 1, 3, 4, 5, 2, 3, 6, 7, 4, 8, 9, 10, 5, 11, 6, 12, 7, 13, 14, 15, 8, 9, 16, 10, 11, 17, 18, 19, 12, 20, 21, 22, 13, 23, 24, 25, 14, 26, 27, 28, 15, 16, 29, 30, 17, 18, 19, 31, 20, 32, 21, 33, 22, 34, 35, 36, 23, 37, 38, 24, 25, 39, 40, 41, 26, 42, 43, 44, 27, 45, 46, 28, 29, 47, 48, 49, 30, 31, 50, 51, 32, 52, 53, 54, 33, 55, 34, 56, 35, 57, 58, 59, 36 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Each number n > 0 occurs exactly twice in this sequence, at the positions A005117(1+n) and A013929(n). LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 FORMULA a(1) = 0; for n > 1, if A008683(n) is 0 [when n is not squarefree], then a(n) = A057627(n), otherwise a(n) = A013928(n). PROG (Scheme) (define (A284584 n) (cond ((= 1 n) 0) ((zero? (A008683 n)) (A057627 n)) (else (A013928 n)))) (Python) from sympy import mobius from sympy.ntheory.factor_ import core def a057627(n): return n - sum([mobius(k)**2 for k in range(1, n + 1)]) def a013928(n): return sum([1 for i in range(1, n) if core(i) == i]) def a(n): if n==1: return 0 if core(n)==n: return a013928(n) else: return a057627(n) print([a(n) for n in range(1, 121)]) # Indranil Ghosh, Apr 17 2017 CROSSREFS Cf. A005117, A008683, A013928, A013929, A057627, A243343, A243345, A243347, A243352. Cf. A066136 (a similar sequence). Sequence in context: A318311 A356294 A338091 * A256100 A340383 A117407 Adjacent sequences: A284581 A284582 A284583 * A284585 A284586 A284587 KEYWORD nonn AUTHOR Antti Karttunen, Apr 17 2017 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.

Last modified December 4 04:32 EST 2023. Contains 367541 sequences. (Running on oeis4.)