A383906 Semiprimes k such that the sums of the even digits of k and of the odd digits of k are equal.

121, 134, 143, 178, 187, 314, 341, 358, 413, 538, 583, 633, 718, 781, 817, 835, 871, 1043, 1267, 1322, 1403, 1469, 1649, 1726, 1762, 1807, 1829, 1982, 2101, 2123, 2167, 2189, 2231, 2321, 2433, 2558, 2563, 2653, 2761, 2855, 2918, 2981, 3063, 3085, 3265, 3287, 3401, 3489, 3603, 3647, 3669, 3746

Offset

1,1

Comments

Semiprimes in A036301.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(3) = 143 is a term because 143 = 11 * 13 is a semiprime and the sum of its even digits (4) and the sum of its odd digits (1 and 3) are both 4.

Maple

filter:= proc(n) local t;
  if numtheory:-bigomega(n) <> 2 then return false fi;
  add(t*(-1)^t, t=convert(n, base, 10)) = 0
end proc:
select(filter, [$100 .. 10000]);

Mathematica

Select[Range[3746], PrimeOmega[#]==2&&Total[Select[IntegerDigits[#], OddQ]]==Total[Select[IntegerDigits[#], EvenQ]]&] (* James C. McMahon, Sep 06 2025 *)

Crossrefs

Intersection of A001358 and A036301,

Cf. A071650, A076167.

Sequence in context: A050697 A319923 A020253 * A182776 A080466 A271630

Adjacent sequences: A383903 A383904 A383905 * A383907 A383908 A383909

Keyword

nonn,base

Author

Zak Seidov and Robert Israel, Sep 05 2025

Status

approved