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!)
 A089166 Number of primes between squares of successive odd numbers. 3
 4, 5, 6, 7, 8, 9, 9, 13, 11, 13, 14, 15, 15, 17, 16, 19, 19, 19, 21, 23, 20, 23, 23, 28, 21, 31, 25, 23, 30, 32, 30, 29, 31, 32, 34, 30, 34, 40, 32, 36, 39, 37, 37, 40, 38, 39, 44, 42, 45, 44, 42, 42, 45, 42, 48, 52, 49, 45, 50, 48, 51, 55, 56, 47, 52, 56, 56, 53, 49, 58, 62, 56 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS As the squares of the successive odd numbers are those numbers appearing on the SE spoke of the Ulam spiral, a(n) also gives the number of primes appearing in the n-th square ring around 1 of the Ulam spiral. - Scott R. Shannon, Jan 14 2020 LINKS Didier van der Straten, Jon Perry, Mark Underwood, TR: [PrimeNumbers] pi(x), digest of 3 messages in primeforms Yahoo group, Aug 29 - Aug 30, 2003. [Cached copy] Mark Underwood, [PrimeNumbers] pi(x). Wikipedia, Ulam Spiral. MATHEMATICA Table[PrimePi[(2n + 1)^2] - PrimePi[(2n - 1)^2], {n, 1, 72}] PROG (PARI) forstep (k=1, 130, 2, print1(primepi((k+2)^2)-primepi(k^2), ", ")) \\ Hugo Pfoertner, Nov 15 2019 (MAGMA) [#[p:p in PrimesInInterval(k^2, (k+2)^2)]:k in [1..150 by 2]]; // Marius A. Burtea, Jan 14 2020 CROSSREFS Cf. A014085, A016754 (odd squares). Sequence in context: A090925 A143836 A168094 * A178052 A030543 A214084 Adjacent sequences:  A089163 A089164 A089165 * A089167 A089168 A089169 KEYWORD nonn AUTHOR Robert G. Wilson v, Dec 06 2003 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 11 03:22 EDT 2020. Contains 336421 sequences. (Running on oeis4.)