A028864 Primes with digits in nondecreasing order.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 37, 47, 59, 67, 79, 89, 113, 127, 137, 139, 149, 157, 167, 179, 199, 223, 227, 229, 233, 239, 257, 269, 277, 337, 347, 349, 359, 367, 379, 389, 449, 457, 467, 479, 499, 557, 569, 577, 599, 677, 1117, 1123, 1129

Offset

1,1

Comments

Identical digits are acceptable, e.g., 1117 is in the sequence. - Harvey P. Dale, Aug 16 2011

Links

Alois P. Heinz, Table of n, a(n) for n = 1..10000 (terms n = 1..1000 from T. D. Noe)

Formula

Trivially, a(n) >> exp(n^(1/10)). - Charles R Greathouse IV, Mar 15 2014

prime(n) = A028905(n) if prime(n) is in this sequence. - Alonso del Arte, Nov 25 2019

Mathematica

daoQ[n_] := Count[Differences[IntegerDigits[n]], _?(# < 0 &)] == 0; Select[Prime[Range[200]], daoQ] (* Harvey P. Dale, Aug 16 2011 *)
Select[Prime[Range[200]], Min[Differences[IntegerDigits[#]]]>-1&] (* Harvey P. Dale, Mar 02 2023 *)

Prog

(R) j=2; y=as.bigz(c()); while(j<1000) {
x=sort(as.numeric(strsplit(as.character(j), spl="")[[1]]), decr=F)
if(j==paste(x[x>0], collapse="")) y=c(y, j)
j=nextprime(j)
} //  Christian N. K. Anderson, Apr 04 2013
(PARI) select(n->n=digits(n); n==vecsort(n), primes(500)) \\ Charles R Greathouse IV, Mar 15 2014
(Magma) [p:p in PrimesUpTo(1200)| Reverse(Intseq(p)) eq Sort(Intseq(p))]; // Marius A. Burtea, Nov 29 2019
(Python)
from itertools import count, islice, combinations_with_replacement
from sympy import isprime
def A028864_gen(): # generator of terms
    yield from (2, 3, 5, 7)
    a, b = {'1':0, '2':1, '3':1, '4':2, '5':2, '6':2, '7':2, '8':3, '9':3}, (1, 3, 7, 9)
    for l in count(1):
        for d in combinations_with_replacement('123456789', l):
            k = 10*int(''.join(d))
            for e in b[a[d[-1]]:]:
                if isprime(m:=k+e):
                    yield m
A028864_list = list(islice(A028864_gen(), 30)) # Chai Wah Wu, Dec 25 2023

Crossrefs

Cf. A009994, A052015, A028867, A052014, A028905.

Sequence in context: A335331 A279956 A197300 * A342063 A067903 A341934

Adjacent sequences: A028861 A028862 A028863 * A028865 A028866 A028867

Keyword

nonn,base,nice

Author

Patrick De Geest

Extensions

Definition corrected by Omar E. Pol, Mar 22 2012

Status

approved