A044023 Numbers k such that 3 and 7 occur juxtaposed in the base-10 representation of k but not of k+1.

37, 73, 137, 173, 237, 273, 337, 379, 437, 473, 537, 573, 637, 673, 739, 773, 837, 873, 937, 973, 1037, 1073, 1137, 1173, 1237, 1273, 1337, 1379, 1437, 1473, 1537, 1573, 1637, 1673, 1739, 1773, 1837, 1873, 1937, 1973, 2037

Offset

1,1

Links

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

Mathematica

SequencePosition[Table[If[SequenceCount[IntegerDigits[n], {3, 7}]>0||SequenceCount[IntegerDigits[n], {7, 3}]>0, 1, 0], {n, 2100}], {1, 0}][[;; , 1]] (* Harvey P. Dale, Jan 28 2026 *)

Crossrefs

Sequence in context: A380943 A039420 A043243 * A179579 A069204 A153208

Adjacent sequences: A044020 A044021 A044022 * A044024 A044025 A044026

Keyword

nonn,base

Author

Clark Kimberling

Status

approved