A382073 Semiprimes with sum of digits 4.

4, 22, 121, 202, 301, 1003, 1111, 2101, 10003, 10021, 10102, 10201, 11002, 11101, 12001, 30001, 100021, 100102, 100201, 101011, 110002, 110101, 111001, 200011, 200101, 1000021, 1000111, 1000201, 1001002, 1001101, 1110001, 2001001, 3000001, 10000003, 10000021, 10000201, 10010002, 10020001

Offset: 1

Author

Zak Seidov and Robert Israel, Mar 14 2025

Keywords

• nonn
• base

Examples

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

Links

• Robert Israel, Table of n, a(n) for n = 1..3655

Crossrefs

Intersection of A001358 and A052218.

Cf. A062339.

Programs

Maple

qsemi:= proc(n) if numtheory:-bigomega(n) = 2 then n fi end proc:
F:= proc(d) local i,j;
   seq(seq(qsemi(10^(d-1)+1 + 10^i + 10^j),i=0..j),j=0..d-1)
end proc:
map(F, [$1..10]);

Mathematica

Select[Range[10^5],PrimeOmega[#]==2 && DigitSum[#]==4 &] (* Stefano Spezia, Mar 14 2025 *)