This site is supported by donations to The OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A168545 Primes p such that the concatenation of p and 29 is a square number: "p 29" = N = m^2. 2
 5, 7, 53, 59, 151, 313, 1069, 1789, 1823, 2237, 2777, 3329, 3881, 3931, 4583, 5227, 6037, 7621, 7691, 9467, 12611, 13759, 14957, 17609, 20249, 28123, 35081, 36979, 49417, 56311, 56501, 63857, 69011, 71663, 79693, 85439, 94433, 114041, 117443 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS (1) It is conjectured that the sequence is infinite. (2) 29 = prime(10) is the smallest prime with the property that its digits can be the final two digits of a square. (3) The possible final digits of m are necessarily e = 23, 27, 73 or 77. (4) Elementary proof of (3) with (10^2 * k + e)^2 = "n 29" for these four values of e only. (5) Note 23 + 77 = 27 + 73 = 10^2. REFERENCES Andreas Bartholome, Josef Rung, Hans Kern: Zahlentheorie für Einsteiger, Vieweg & Sohn 1995 Leonard E. Dickson: History of the Theory of numbers, vol. I, Dover Publications 2005 Theo Kempermann, Zahlentheoretische Kostproben, Harri Deutsch, 2. aktualisierte Auflage 2005 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE (1) 529 = 23^2, 5 = prime(3) = a(1); (2) 729 = 27^2, 7 = prime(4) = a(2); (3) 5329 = 73^2, 53 = prime(16) = a(3); (4) 16129 = 127^2, but 161 = 7 * 23 is composite => 161 is not a term of the sequence; (5) 31329 = 177^2, 313 = prime(65) gives a(6) = 313. MAPLE A:= NULL: count:= 0: for m from 0 while count < 100 do   for q in [23, 27, 73, 77] do     r:= floor((100*m + q)^2/100);     if isprime(r) then A:= A, r; count:= count+1; fi od od: A; # Robert Israel, Nov 23 2015 PROG (PARI) a(n) = isprime(n) && issquare(100*n + 29) \\ Michel Marcus, Jul 22 2013 CROSSREFS Cf. A000040 (the prime numbers). Cf. A167535 (concatenation of two square numbers which give a prime). Cf. A158896 (primes whose squares are a concatenation of 2 with some prime). Sequence in context: A210244 A123789 A180552 * A320116 A320108 A320112 Adjacent sequences:  A168542 A168543 A168544 * A168546 A168547 A168548 KEYWORD nonn,base AUTHOR Ulrich Krug (leuchtfeuer37(AT)gmx.de), Nov 29 2009 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 November 13 00:25 EST 2019. Contains 329083 sequences. (Running on oeis4.)