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 A161786 Primes with at least one digit appearing exactly four times in the decimal expansion. 5

%I #9 Feb 21 2019 23:14:55

%S 10111,11113,11117,11119,11131,11161,11171,11311,11411,16111,22229,

%T 23333,31333,33331,33343,33353,33533,38333,44449,47777,49999,59999,

%U 67777,71777,76777,77377,77477,77747,77773,77797,77977,79777,79999,88883,94999,97777

%N Primes with at least one digit appearing exactly four times in the decimal expansion.

%C The sequence is probably infinite.

%H Harvey P. Dale, <a href="/A161786/b161786.txt">Table of n, a(n) for n = 1..2000</a>

%e 101117 has exactly four 1s.

%p isdgctm := proc(n,d) local dgs,a,i ; dgs := convert(n,base,10) ; a := [seq(0,j=0..9)] ;

%p 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:

%p for n from 1 to 10000 do p := ithprime(n) ; if isdgctm(p,4) then printf("%d,",p) ; fi; od: # _R. J. Mathar_, Jun 21 2009

%t Select[Prime[Range[186,10000]],MemberQ[DigitCount[#],4]&] (* _Harvey P. Dale_, Apr 12 2015 *)

%K nonn,base

%O 1,1

%A _Ki Punches_, Jun 19 2009

%E Edited and corrected by _R. J. Mathar_, Jun 21 2009

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Last modified August 11 04:26 EDT 2024. Contains 375059 sequences. (Running on oeis4.)