A145908 - OEIS

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A145908

Primes p such that p + floor(sqrt(p)) OR p + ceiling(sqrt(p)) is also prime.

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