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A145908 Primes p such that p + floor(sqrt(p)) OR p + ceiling(sqrt(p)) is also prime. 1
2, 3, 5, 13, 19, 31, 37, 41, 47, 53, 59, 71, 97, 103, 127, 137, 139, 151, 167, 179, 197, 241, 277, 293, 313, 331, 349, 389, 401, 419, 457, 487, 499, 547, 563, 569, 577, 593, 607, 617, 619, 647, 683, 701, 733, 769, 811, 829, 853, 857, 877, 881, 907, 911, 937 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

FORMULA

A145907 UNION A086085. - R. J. Mathar, Oct 31 2008

EXAMPLE

p = 3; 3 + ceiling(sqrt(3)) = 5, which is prime. p = 5; 5 + floor(sqrt(5)) = 7, which is prime.

MAPLE

for n from 1 to 820 do p := ithprime(n) ; f := p+floor(sqrt(p)) ; c := p+ceil(sqrt(p)) ; if isprime(f) or isprime(c) then printf("%d, ", p) ; fi; od: # R. J. Mathar, Oct 31 2008

CROSSREFS

Cf. A145907, A086085.

Sequence in context: A155738 A215371 A164958 * A173830 A224223 A238497

Adjacent sequences:  A145905 A145906 A145907 * A145909 A145910 A145911

KEYWORD

nonn

AUTHOR

Kyle D. Balliet, Oct 24 2008, Nov 06 2008

EXTENSIONS

2 terms inserted and sequence extended by R. J. Mathar, Oct 31 2008

STATUS

approved

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Last modified July 31 18:23 EDT 2021. Contains 346376 sequences. (Running on oeis4.)