A043248 Numbers k such that 4 and 7 occur juxtaposed in the base-10 representation of k but not of k-1.

47, 74, 147, 174, 247, 274, 347, 374, 447, 470, 547, 574, 647, 674, 740, 774, 847, 874, 947, 974, 1047, 1074, 1147, 1174, 1247, 1274, 1347, 1374, 1447, 1470, 1547, 1574, 1647, 1674, 1740, 1774, 1847, 1874, 1947, 1974, 2047

Offset

1,1

Links

Table of n, a(n) for n=1..41.

Mathematica

SequencePosition[Table[If[SequenceCount[IntegerDigits[n], {4, 7}]>0 || SequenceCount[ IntegerDigits[n], {7, 4}]>0, 1, 0], {n, 2100}], {0, 1}][[All, 2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 20 2019 *)

Crossrefs

Sequence in context: A338273 A165335 A039425 * A044028 A126095 A132259

Adjacent sequences: A043245 A043246 A043247 * A043249 A043250 A043251

Keyword

nonn,base

Author

Clark Kimberling

Status

approved