A061371 - OEIS

%I #16 Sep 08 2022 08:45:03

%S 22,25,27,32,33,35,52,55,57,72,75,77,222,225,232,235,237,252,253,255,

%T 272,273,275,322,323,325,327,332,333,335,352,355,357,372,375,377,522,

%U 525,527,532,533,535,537,552,553,555,572,573,575,722,723,725,732,735

%N Composite numbers with all prime digits.

%H T. D. Noe, <a href="/A061371/b061371.txt">Table of n, a(n) for n = 1..1000</a>

%e a(5) = 35 is composite with digits 3 and 5 which are primes.

%e 22 is nonprime and has prime digits, twice 2;

%e 573 is nonprime and has prime digits, 3, 5 and 7.

%p 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:

%p ts_stnepf:=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))='false') then stpf:=stpf+1; # number of nonprime digits fi od; RETURN(stpf) end:

%p ts_nepr_neprn0:=proc(n) local i, stpf, ans, ans1, tren; ans:=[ ]: stpf:=0: tren:=1: for i from 1 to n do if ( isprime(i)='false' and ts_stnepf(i) = 0) then ans:=[ op(ans), i ]: tren:=tren+1; fi od; RETURN(ans) end: ts_nepr_neprn0(4000); # _Jani Melik_, Apr 11 2004

%t With[{comps=Complement[Range[1000],Prime[Range[PrimePi[1000]]]]}, Select[ comps, And@@PrimeQ[IntegerDigits[#]]&]] (* _Harvey P. Dale_, Dec 21 2011 *)

%t Table[Select[FromDigits/@Tuples[{2,3,5,7},n],CompositeQ],{n,2,4}]//Flatten (* _Harvey P. Dale_, Oct 05 2019 *)

%o (Magma) [ n: n in [22..736] | not IsPrime(n) and Set(Intseq(n)) subset [2,3,5,7] ];  // _Bruno Berselli_, Dec 21 2011

%Y Cf. A061372.

%K nonn,base

%O 1,1

%A _Amarnath Murthy_, May 02 2001

%E Corrected and extended by Larry Reeves (larryr(AT)acm.org), May 08 2001