A083004 Primes whose 10's complement is a square.

19, 271, 919, 991, 15319, 22159, 25471, 28711, 46639, 54631, 64279, 74719, 84871, 86311, 87679, 90199, 92431, 95239, 98479, 98911, 99559, 99991, 1125559, 1196911, 1338751, 1549351, 1653679, 1688311, 1826119, 1996759, 2064511, 2098279

Offset

1,1

Links

Table of n, a(n) for n=1..32.

Example

a(5)=15319 because 100000-15319 = 84681 = 291^2.

Mathematica

Select[Prime[Range[160000]], IntegerQ[Sqrt[10^IntegerLength[#]-#]]&] (* Harvey P. Dale, May 24 2011 *)

Prog

(PARI) { PTS(m)=local(ct, sr, ptc); ct=0; sr=0; forprime(p=2, m, ptc=10^length(Str(p))-p; if(issquare(ptc), ct+=1; print1(p", "); sr+=1.0/p; )); print(); print("Found "ct" primes < "m); print("Sum of reciprocals = "sr); }

Crossrefs

Sequence in context: A141942 A181043 A142899 * A139739 A016189 A125476

Adjacent sequences: A083001 A083002 A083003 * A083005 A083006 A083007

Keyword

nonn,base

Author

Jason Earls, May 30 2003

Status

approved