A116066 Numbers k such that both k and the k-th prime have nondecreasing digits.

1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 15, 17, 19, 22, 24, 33, 34, 35, 37, 39, 46, 48, 49, 55, 57, 59, 68, 69, 77, 88, 123, 188, 189, 222, 229, 237, 239, 246, 247, 249, 266, 278, 333, 336, 337, 345, 346, 348, 355, 357, 367, 388, 477, 489, 499, 669, 1117, 1346, 1347, 1348

Offset

1,2

Links

Michael S. Branicky, Table of n, a(n) for n = 1..97 (all terms < 10^9)

Example

p(237) = 1489.

Mathematica

Select[Range[1500], Min[Differences[IntegerDigits[#]]]>=0&&Min[ Differences[ IntegerDigits[Prime[#]]]]>=0&] (* Harvey P. Dale, May 14 2019 *)

Prog

(Python)
from sympy import sieve
from itertools import count, islice, combinations_with_replacement as mc
def nd(n): s = str(n); return s == "".join(sorted(s))
def bgen(d): yield from map(int, ("".join(m) for m in mc("123456789", d)))
def agen():
    for d in count(1):
        yield from (k for k in bgen(d) if nd(sieve[k]))
print(list(islice(agen(), 60))) # Michael S. Branicky, Jun 26 2022

Crossrefs

Cf. A116067, A116068, A116069.

Sequence in context: A171827 A322002 A107743 * A261874 A334929 A008816

Adjacent sequences: A116063 A116064 A116065 * A116067 A116068 A116069

Keyword

nonn,base

Author

Giovanni Resta, Feb 13 2006

Status

approved