A382073 - OEIS

%I #8 Mar 14 2025 20:23:29

%S 4,22,121,202,301,1003,1111,2101,10003,10021,10102,10201,11002,11101,

%T 12001,30001,100021,100102,100201,101011,110002,110101,111001,200011,

%U 200101,1000021,1000111,1000201,1001002,1001101,1110001,2001001,3000001,10000003,10000021,10000201,10010002,10020001

%N Semiprimes with sum of digits 4.

%H Robert Israel, <a href="/A382073/b382073.txt">Table of n, a(n) for n = 1..3655</a>

%e a(3) = 121 is a term because 121 = 11^2 is a semiprime and its sum of digits is 1+2+1=4.

%p qsemi:= proc(n) if numtheory:-bigomega(n) = 2 then n fi end proc:

%p F:= proc(d) local i,j;

%p    seq(seq(qsemi(10^(d-1)+1 + 10^i + 10^j),i=0..j),j=0..d-1)

%p end proc:

%p map(F, [$1..10]);

%t Select[Range[10^5],PrimeOmega[#]==2 && DigitSum[#]==4 &] (* _Stefano Spezia_, Mar 14 2025 *)

%Y Intersection of A001358 and A052218.

%Y Cf. A062339.

%K nonn,base

%O 1,1

%A _Zak Seidov_ and _Robert Israel_, Mar 14 2025