A043506 Numbers having two 4's in base 10.

44, 144, 244, 344, 404, 414, 424, 434, 440, 441, 442, 443, 445, 446, 447, 448, 449, 454, 464, 474, 484, 494, 544, 644, 744, 844, 944, 1044, 1144, 1244, 1344, 1404, 1414, 1424, 1434, 1440, 1441, 1442, 1443, 1445, 1446, 1447, 1448

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base

Links

• Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A043498.

Subsequence of A011534.

Programs

Mathematica

Select[Range[100000], DigitCount[#, 10, 4] == 2 &] (* Vincenzo Librandi, Nov 20 2015 *)

PARI

c(k, d, b) = {my(c=0, f); while (k>b-1, f=k-b*(k\b); if (f==d, c++); k\=b); if (k==d, c++); return(c)}
for(n=0, 2000, if(c(n, 4, 10)==2, print1(n, ", "))) \\ Altug Alkan, Nov 20 2015