A231170 - OEIS

A231170

Semiprimes with equal number of even and odd digits.

10, 14, 21, 25, 34, 38, 49, 58, 65, 69, 74, 85, 87, 94, 1003, 1007, 1018, 1027, 1041, 1043, 1047, 1067, 1081, 1094, 1126, 1142, 1186, 1203, 1205, 1207, 1214, 1227, 1234, 1238, 1241, 1243, 1247, 1261, 1263, 1267, 1285, 1294, 1306, 1322, 1346, 1366, 1382, 1401

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OFFSET

1,1

COMMENTS

This is to A144226 as semiprimes A001358 are to primes A000040.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000

FORMULA

A001358 INTERSECTION A227870.

MATHEMATICA

semiPrimeQ[n_Integer] := If[Abs[n] < 2, False, (2 == Plus @@ Transpose[FactorInteger[Abs[n]]][[2]])]; fQ[n_] := Module[{d = IntegerDigits[n], len}, len = Length[d]; EvenQ[len] && len == 2*Count[d, _?(EvenQ[#] &)]]; Select[Range[2500], semiPrimeQ[#] && fQ[#] &] (* T. D. Noe, Nov 07 2013 *)

Select[Range[2500], PrimeOmega[#]==2&&Count[IntegerDigits[#], _?OddQ] == IntegerLength[#]/2&] (* Harvey P. Dale, May 05 2014 *)

CROSSREFS

Cf. A001358, A030141, A031443, A144226, A227870.

Sequence in context: A325161 A175586 A089995 * A348306 A337709 A063764

Adjacent sequences: A231167 A231168 A231169 * A231171 A231172 A231173

KEYWORD

nonn,base,easy

AUTHOR

Jonathan Vos Post, Nov 04 2013

EXTENSIONS

More terms from Alois P. Heinz, Nov 07 2013

STATUS

approved