|
|
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]
|
|
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
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|