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A092629
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Numbers that have a nonprime number of prime digits.
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2
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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 24, 26, 28, 29, 30, 31, 34, 36, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 54, 56, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 74, 76, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88
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OFFSET
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1,2
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LINKS
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EXAMPLE
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24 has one prime digit 2 and their number 1 is nonprime;
235719 has four prime digits 2,3,5,7 and their number 4 is nonprime.
313 is not in the sequence as it has a prime number (2) of prime digits (3, 3). - David A. Corneth, Aug 09 2023
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MAPLE
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stev_sez:=proc(n) local i, tren, st, ans, anstren; ans:=[ ]: anstren:=[ ]: tren:=n: for i while (tren>0) do st:=round( 10*frac(tren/10) ): ans:=[ op(ans), st ]: tren:=trunc(tren/10): end do; for i from nops(ans) to 1 by -1 do anstren:=[ op(anstren), op(i, ans) ]; od; RETURN(anstren); end: ts_stpf:=proc(n) local i, stpf, ans; ans:=stev_sez(n): stpf:=0: for i from 1 to nops(ans) do if (isprime(op(i, ans))='true') then stpf:=stpf+1; # number of prime digits fi od; RETURN(stpf) end: ts_nepr:=proc(n) local i, stpf, ans, ans1; ans:=[ ]: stpf:=0: for i from 1 to n do if (isprime( ts_stpf(i) )='false') then ans:=[ op(ans), i ]: fi od; RETURN(ans) end: ts_nepr(600);
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MATHEMATICA
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Select[Range[100], !PrimeQ[Count[IntegerDigits[#], _?PrimeQ]]&] (* Harvey P. Dale, Jan 15 2013 *)
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CROSSREFS
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KEYWORD
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nonn,easy,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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