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Primes with digits in nonincreasing order.
11

%I #27 Dec 26 2023 06:41:22

%S 2,3,5,7,11,31,41,43,53,61,71,73,83,97,211,311,331,421,431,433,443,

%T 521,541,631,641,643,653,661,733,743,751,761,773,811,821,853,863,877,

%U 881,883,887,911,941,953,971,977,983,991,997,2111,2221,3221

%N Primes with digits in nonincreasing order.

%H Alois P. Heinz, <a href="/A028867/b028867.txt">Table of n, a(n) for n = 1..10000</a> (terms n = 1..1000 from T. D. Noe)

%t t={};Do[p=Prime[n];If[Select[Differences[IntegerDigits[p]],#>0&]=={},AppendTo[t,p]],{n,460}];t (* _Jayanta Basu_, May 04 2013 *)

%t Select[Prime[Range[600]],Max[Differences[IntegerDigits[#]]]<1&] (* _Harvey P. Dale_, Oct 30 2013 *)

%o (PARI) is(n)=my(d=digits(n)); for(i=2,#d,if(d[i]>d[i-1],return(0))); isprime(n) \\ _Charles R Greathouse IV_, Aug 18 2017

%o (Python)

%o from itertools import count, islice, combinations_with_replacement

%o from sympy import isprime

%o def A028867_gen(): # generator of terms

%o yield from (2,3,5,7)

%o a, b = {'1':1,'2':1,'3':2,'4':2,'5':2,'6':2,'7':3,'8':3,'9':4}, (1,3,7,9)

%o for l in count(1):

%o mlist = []

%o for d in combinations_with_replacement('987654321',l):

%o k = 10*int(''.join(d))

%o for e in b[:a[d[-1]]]:

%o if isprime(m:=k+e):

%o mlist.append(m)

%o yield from sorted(mlist)

%o A028867_list = list(islice(A028867_gen(),30)) # _Chai Wah Wu_, Dec 25 2023

%Y Cf. A052014, A028864, A052015.

%K nonn,base

%O 1,1

%A _Patrick De Geest_

%E Definition corrected by _Omar E. Pol_, Mar 22 2012