A161848 Primes with at least one digit appearing exactly three times in the decimal expansion.

1117, 1151, 1171, 1181, 1511, 1777, 1811, 1999, 2111, 2221, 2333, 2777, 2999, 3313, 3323, 3331, 3343, 3373, 3433, 3533, 3733, 3833, 4111, 4441, 4447, 4999, 5333, 5557, 6661, 7177, 7333, 7477, 7577, 7717, 7727, 7757, 7877, 8111, 8887, 8999, 9199, 9929

Offset

1,1

Comments

Sequence is probably infinite.

Links

Table of n, a(n) for n=1..42.

Example

2333, 3313, 3833 all repeat some digit 3 three times.

Maple

isdgctm := proc(n, d) local dgs, a, i ; dgs := convert(n, base, 10) ; a := [seq(0, j=0..9)] ;
for i in dgs do a := subsop(i+1=op(i+1, a)+1, a) ; od: if convert(a, set) intersect {d} <> {} then true; else false; fi; end:
for n from 1 to 2000 do p := ithprime(n) ; if isdgctm(p, 3) then printf("%d, ", p) ; fi; od: # R. J. Mathar, Jun 21 2009

Crossrefs

Cf. A161786, A161796.

Sequence in context: A260103 A258691 A221428 * A020380 A243527 A251360

Adjacent sequences: A161845 A161846 A161847 * A161849 A161850 A161851

Keyword

nonn,base

Author

Ki Punches, Jun 20 2009

Extensions

Edited and corrected by R. J. Mathar, Jun 21 2009

Status

approved