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A048420
Primes whose consecutive digits differ by 8 or 9.
8
2, 3, 5, 7, 19, 191, 809, 919, 9091, 80809, 80909, 91909, 190909, 909091, 1908091, 1909091, 9090919, 9091909, 19090909, 80919191, 190909091, 191908091, 809080919, 809191919, 908080909, 919080919, 919191919, 1909080809
OFFSET
1,1
LINKS
MAPLE
extend:= proc(n) local d, x;
d:= n mod 10;
seq(10*n+x, x = select(t -> t >= 0 and t <= 9, [d-9, d-8, d+8, d+9]))
end proc:
R:= 2, 3, 5, 7: count:= 4:
T:= [$1..9]:
for d from 2 while count < 100 do
T:= map(extend, T);
V:= select(isprime, T);
count:= count+nops(V);
R:= R, op(V);
od:
R; # Robert Israel, Oct 17 2023
MATHEMATICA
Join[{2, 3, 5, 7}, Select[FromDigits/@Tuples[{0, 1, 8, 9}, 10], PrimeQ[#] && AllTrue[ Abs[ Differences[ IntegerDigits[#]]], #>7&]&]] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Oct 08 2017 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Apr 15 1999
EXTENSIONS
More terms from Naohiro Nomoto, Jul 28 2001
STATUS
approved