A092623 Primes with exactly three prime digits.

223, 227, 233, 257, 277, 337, 353, 373, 523, 557, 577, 727, 733, 757, 773, 1223, 1237, 1277, 1327, 1373, 1523, 1553, 1723, 1733, 1753, 1777, 2027, 2053, 2137, 2153, 2203, 2207, 2213, 2221, 2239, 2243, 2251, 2267, 2287, 2293, 2297, 2339, 2347, 2351, 2371

Offset

1,1

Links

Table of n, a(n) for n=1..45.

Formula

a(n) >> x^1.285

Example

223 is prime and it has three prime digits 2,2,3;
1237 is prime and it has three prime digits 2,3,7;

Maple

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_pr_prnt:=proc(n) local i, stpf, ans, ans1, tren; ans:=[ ]: stpf:=0: tren:=1: for i from 1 to n do if ( isprime(i)='true' and ts_stpf(i) = 3) then ans:=[ op(ans), i ]: tren:=tren+1; fi od; RETURN(ans) end: ts_pr_prnt(5000);

Mathematica

Select[Prime[Range[400]], Count[IntegerDigits[#], _?PrimeQ]==3&] (* Harvey P. Dale, Dec 27 2011 *)

Crossrefs

Cf. A034844, A019546.

Sequence in context: A243766 A153424 A100607 * A220474 A243767 A345533

Adjacent sequences: A092620 A092621 A092622 * A092624 A092625 A092626

Keyword

nonn,base

Author

Jani Melik, Apr 11 2004

Status

approved