A095976 Numbers k such that (largest digit of k) + (largest digit of k+1) is prime.

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, 46, 48, 55, 56, 58, 66, 68, 78, 79, 88, 100, 101, 102, 103, 105, 106, 108, 110, 111, 112, 113, 115, 116, 118, 119, 122, 123, 125, 126, 128, 133, 135, 136, 138, 139, 145, 146

Offset

1,2

Comments

No terms contain digit 9 before a non-9. - Robert Israel, May 20 2020

Links

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

Example

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

Maple

N:= 500: # to get terms <= N
L:= map(t -> max(convert(t, base, 10)), [$1..N+1]):
LL:= L[1..-2]+L[2..-1]:
select(t -> member(LL[t], {2, 3, 5, 7, 11, 13, 17}), [$1..N]); # Robert Israel, May 20 2020

Mathematica

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 *)

Prog

(PARI) isok(m) = isprime(vecmax(digits(m))+vecmax(digits(m+1))); \\ Michel Marcus, May 20 2020
(Python)
def ok(n): return int(max(str(n))) + int(max(str(n+1))) in {2, 3, 5, 7, 11, 13, 17}
print([k for k in range(147) if ok(k)]) # Michael S. Branicky, Aug 03 2022

Crossrefs

Cf. A054055.

Sequence in context: A028755 A187897 A187319 * A187899 A024609 A167056

Adjacent sequences: A095973 A095974 A095975 * A095977 A095978 A095979

Keyword

base,easy,nonn

Author

Jason Earls, Jul 16 2004

Status

approved