Tetradic Number

Author

Eric W. Weisstein
March 1, 2009

This notebook downloaded from http://mathworld.wolfram.com/notebooks/IntegerSequences/TetradicNumber.nb.

For more information, see Eric's MathWorld entry http://mathworld.wolfram.com/TetradicNumber.html.

©2009 Wolfram Research, Inc. except for portions noted otherwise

Code

TetradicQ[n_]:=Module[{d=IntegerDigits[n]},
d==Reverse[d]&&Complement[Union[d],{0,1,8}]=={}
]

Enumeration

Select[Range[10^5],TetradicQ]

Short[tetradics=FromDigits/@Select[IntegerDigits/@FromDigits/@Flatten[Outer[List,Sequence@@Table[{0,1,8},{11}]],10],#==Reverse[#]&]]//Timing

Primes

Take[Select[tetradics,PrimeQ],10]

Carmody 2006

P. Carmody, pers. comm.
Jan. 7, 2006

TetradicQ[carmody=10^127576+1081101080188810801011801*10^63776+1]

IntegerLength[carmody]

Darren Bedwell September 28, 2008

pt=10^130048+(9*10^37077-2)/11*10^46486+1;

TetradicQ[pt]

IntegerLength[pt]