A382465 Positive integers such that every even digit except the first is immediately preceded by a smaller digit.

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 24, 25, 26, 27, 28, 29, 31, 33, 34, 35, 36, 37, 38, 39, 41, 43, 45, 46, 47, 48, 49, 51, 53, 55, 56, 57, 58, 59, 61, 63, 65, 67, 68, 69, 71, 73, 75, 77, 78, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99

Offset

1,2

Comments

Conjecture: these are the terms of A382462, sorted.

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Mathematica

A382465Q[k_] := FreeQ[Partition[IntegerDigits[k], 2, 1], {i_, j_?EvenQ} /; i >= j];
Select[Range[100], A382465Q]

Prog

(Python)
def ok(n):
    s = str(n)
    return n and all(d not in "02468" or s[i-1]<d for i, d in enumerate(s) if i > 0)
print([k for k in range(100) if ok(k)]) # Michael S. Branicky, Apr 30 2025

Crossrefs

Cf. A382462, A382464 (complement).

Cf. A377912, A382624, A382938, A383062, A383246, A383248, A383250, A383501.

Sequence in context: A090274 A385324 A254621 * A383246 A227510 A032898

Adjacent sequences: A382462 A382463 A382464 * A382466 A382467 A382468

Keyword

nonn,base,easy

Author

Paolo Xausa, Mar 28 2025

Status

approved