|
Search: id:A096246
|
|
|
| A096246 |
|
Base-2 deletable primes (written in base 10). |
|
+0
16
|
|
| 2, 3, 5, 7, 11, 13, 19, 23, 29, 37, 43, 47, 53, 59, 61, 73, 79, 83, 101, 107, 109, 137, 149, 151, 157, 163, 167, 173, 179, 197, 211, 229, 277, 281, 293, 307, 311, 313, 317, 331, 347, 349, 359, 389, 397, 419, 421, 457, 461, 467, 557, 563, 569, 587, 599, 601, 613
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
A prime p is a base-b deletable prime if when written in base b it has the property that removing some digit leaves either the empty string or another deletable prime. However, in base 2 we adopt the convention that 2 = 10 and 3 = 11 are deletable.
Deleting a digit cannot leave any leading zeros in the new string. For example, deleting the 2 in 2003 to obtain 003 is not allowed.
|
|
MAPLE
|
isDel := proc(n::integer) local b2, redu, rpr, d; if n = 2 or n =3 then RETURN(true); elif not isprime(n) then RETURN(false); else b2 := convert(n, base, 2); for d from 1 to nops(b2) do redu := [op(1..d-1, b2), op(d+1..nops(b2), b2) ]; if op(nops(redu), redu) = 1 then rpr := sum( op(i, redu)*2^(i-1), i=1..nops(redu)); if isDel(rpr) then RETURN(true); fi; fi; od; RETURN(false); fi; end: for n from 1 to 200 do if isDel(ithprime(n)) then printf("%d, ", ithprime(n)); fi; od: - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 25 2006
|
|
CROSSREFS
|
Cf. A080608, A080603, A096235-A096245.
Sequence in context: A005728 A049643 A050437 this_sequence A106639 A078334 A108696
Adjacent sequences: A096243 A096244 A096245 this_sequence A096247 A096248 A096249
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Michael Kleber (michael.kleber(AT)gmail.com), Feb 28 2003
|
|
EXTENSIONS
|
More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 25 2006
|
|
|
Search completed in 0.002 seconds
|
