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 A116066 Numbers k such that both k and the k-th prime have nondecreasing digits. 4

%I #12 Jun 27 2022 15:59:37

%S 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,

%T 68,69,77,88,123,188,189,222,229,237,239,246,247,249,266,278,333,336,

%U 337,345,346,348,355,357,367,388,477,489,499,669,1117,1346,1347,1348

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

%H Michael S. Branicky, <a href="/A116066/b116066.txt">Table of n, a(n) for n = 1..97</a> (all terms < 10^9)

%e p(237) = 1489.

%t Select[Range[1500],Min[Differences[IntegerDigits[#]]]>=0&&Min[ Differences[ IntegerDigits[Prime[#]]]]>=0&] (* _Harvey P. Dale_, May 14 2019 *)

%o (Python)

%o from sympy import sieve

%o from itertools import count, islice, combinations_with_replacement as mc

%o def nd(n): s = str(n); return s == "".join(sorted(s))

%o def bgen(d): yield from map(int, ("".join(m) for m in mc("123456789", d)))

%o def agen():

%o for d in count(1):

%o yield from (k for k in bgen(d) if nd(sieve[k]))

%o print(list(islice(agen(), 60))) # _Michael S. Branicky_, Jun 26 2022

%Y Cf. A116067, A116068, A116069.

%K nonn,base

%O 1,2

%A _Giovanni Resta_, Feb 13 2006

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Last modified September 16 23:59 EDT 2024. Contains 375984 sequences. (Running on oeis4.)