A173056 Numbers of the form a^b+b^a, a and b are primes.

8, 17, 54, 57, 177, 368, 2169, 2530, 6250, 8361, 94932, 131361, 178478, 524649, 1596520, 1647086, 8389137, 48989176, 129145076, 536871753, 1162268326, 1221074418, 1996813914, 2147484609, 94143190994, 96951758924, 137438954841

Offset

1,1

Comments

2^2+2^2=8, 2^3+3^2=17, 3^3+3^3=54, 2^5+5^2=57, 2^7+7^2=177, 3^5+5^3=368,..

Links

Table of n, a(n) for n=1..27.

Mathematica

nMax=10^12; lim=PrimePi[Log[2, nMax]]; f[a_, b_]:=Prime[a]^Prime[b] + Prime[b]^Prime[a]; Select[Union[Flatten[Table[f[a, b], {a, lim}, {b, lim}]]], #<=nMax&]
nMax=10^12; lim=PrimePi[Log[2, nMax]]; Select[Union[First[#]^Last[#] + Last[#]^First[#]&/@ Tuples[Prime[Range[lim]], {2}]], #<=nMax&]  (* Harvey P. Dale, Mar 12 2011 *)

Crossrefs

Cf. A076980, A173054, A173055.

Sequence in context: A329768 A153873 A111325 * A008782 A146078 A097058

Adjacent sequences: A173053 A173054 A173055 * A173057 A173058 A173059

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Feb 08 2010

Status

approved