A095976 - OEIS

%I #20 Aug 03 2022 10:38:27

%S 1,2,3,5,6,8,10,11,12,13,15,16,18,19,22,23,25,26,28,33,35,36,38,39,45,

%T 46,48,55,56,58,66,68,78,79,88,100,101,102,103,105,106,108,110,111,

%U 112,113,115,116,118,119,122,123,125,126,128,133,135,136,138,139,145,146

%N Numbers k such that (largest digit of k) + (largest digit of k+1) is prime.

%C No terms contain digit 9 before a non-9. - _Robert Israel_, May 20 2020

%H Robert Israel, <a href="/A095976/b095976.txt">Table of n, a(n) for n = 1..10000</a>

%e 12348 is in the sequence because 8 (its largest digit) plus 9 (the largest digit of 12349) equals 17 (a prime).

%p N:= 500: # to get terms <= N

%p L:= map(t -> max(convert(t,base,10)), [$1..N+1]):

%p LL:= L[1..-2]+L[2..-1]:

%p select(t -> member(LL[t], {2, 3, 5, 7, 11, 13, 17}), [$1..N]); # _Robert Israel_, May 20 2020

%t ldQ[n_]:=Module[{ldn=Max[IntegerDigits[n]],ldn1=Max[IntegerDigits[ n+1]]}, PrimeQ[ldn+ldn1]]; Select[Range[150],ldQ]  (* _Harvey P. Dale_, Apr 29 2011 *)

%o (PARI) isok(m) = isprime(vecmax(digits(m))+vecmax(digits(m+1))); \\ _Michel Marcus_, May 20 2020

%o (Python)

%o def ok(n): return int(max(str(n))) + int(max(str(n+1))) in {2, 3, 5, 7, 11, 13, 17}

%o print([k for k in range(147) if ok(k)]) # _Michael S. Branicky_, Aug 03 2022

%Y Cf. A054055.

%K base,easy,nonn

%O 1,2

%A _Jason Earls_, Jul 16 2004