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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A335716 a(n) = pi(pi(n)) - pi(Sum_{k=1..n-1} a(k)) with a(1) = 0. 1
 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1 COMMENTS Conjecture: a(n) hits every nonnegative integer. LINKS Altug Alkan, Table of n, a(n) for n = 1..10000 Altug Alkan, Andrew R. Booker, and Florian Luca, On a recursively defined sequence involving the prime counting function, arXiv:2006.08013 [math.NT], 2020. EXAMPLE a(10861) = pi(pi(10861)) - pi(Sum_{k=1..10860} a(k))) = 216 - 214 = 2. MATHEMATICA a[1] = s[1] = 0; a[n_] := a[n] = PrimePi@ PrimePi@ n - PrimePi@ s[n-1]; s[n_] := s[n] = s[n-1] + a[n]; Array[a, 100] (* Giovanni Resta, Jun 19 2020 *) PROG (PARI) a=vector(10^2); a[1] = 0; for(n=2, #a, a[n] = primepi(primepi(n)) - primepi(sum(k=1, n-1, a[k]))); a CROSSREFS Cf. A000720, A335294. Sequence in context: A180433 A165560 A014306 * A138150 A271591 A287790 Adjacent sequences:  A335713 A335714 A335715 * A335718 A335719 A335720 KEYWORD nonn AUTHOR Altug Alkan, Jun 18 2020 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.

Last modified August 13 22:57 EDT 2020. Contains 336473 sequences. (Running on oeis4.)