A378775 Prime numbers with monotonically decreasing digits, differing by at most 1.

2, 3, 5, 7, 11, 43, 211, 433, 443, 877, 887, 2111, 2221, 3221, 5443, 8887, 9887, 22111, 33211, 43321, 54443, 65543, 76543, 98887, 99877, 322111, 332221, 443221, 444443, 766543, 888887, 988877, 2221111, 3221111, 3222211, 3222221, 3333221, 4322221, 4433333, 4443221

Offset: 1

Author

Randy L. Ekl, Dec 06 2024

Keywords

• nonn
• base
• look

Examples

			211 is a term since 211 is a prime number, the digits of 211 are monotonically decreasing, and the difference between consecutive digits is at most 1.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Primes in A378808.

Cf. A378774, A028864.

Programs

Maple

extend:= proc(x) local d,s,i;
  d:= ilog10(x);
  s:= floor(x/10^d);
  seq(10^(d+1)*i+x, i=s .. min(9,s+1))
end proc:
R:= 2,3,5,7: count:= 4:
M:= [1,3,7,9];
for d from 2 while count < 100 do
  M:= map(extend,M):
  S:= sort(select(isprime,M));
  count:= count+nops(S);
  R:= R,op(S);
od:
R; # Robert Israel, Feb 09 2025

Mathematica

Select[Prime[Range[312218]],ContainsOnly[Drop[IntegerDigits[#],-1]-Rest[IntegerDigits[#]],{0,1}]&] (* James C. McMahon, Dec 21 2024 *)

PARI

isok(p) = if (isprime(p), my(d=digits(p), dd = vector(#d-1, k, d[k+1]-d[k])); (#dd==0) || ((vecmin(dd)>=-1) && (vecmax(dd)<=0))); \\ Michel Marcus, Dec 09 2024