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

1,1

Links

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

Example

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

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 *)

Crossrefs

Intersection of A001358 and A052218.

Cf. A062339.

Sequence in context: A261193 A390423 A025569 * A098834 A065983 A236576

Adjacent sequences: A382070 A382071 A382072 * A382074 A382075 A382076

Keyword

nonn,base

Author

Zak Seidov and Robert Israel, Mar 14 2025

Status

approved