A068990 Primes which remain prime after each digit is increased by 2.

3, 5, 19, 31, 37, 61, 67, 79, 127, 131, 137, 139, 151, 157, 167, 179, 197, 211, 227, 241, 257, 277, 347, 359, 397, 409, 419, 421, 431, 461, 479, 491, 509, 521, 547, 587, 601, 607, 617, 619, 631, 641, 661, 719, 739, 761, 769, 787, 809, 811, 827, 859, 881, 907

Offset

1,1

Links

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

Example

Increasing each digit of the prime 139 by 2 gives 3511, which is also prime; so 139 is a term of the sequence.

Maple

filter:= proc(n) local L, i;
if not isprime(n) then return false fi;
L:= map(t -> `if`(t>=8, op([t-8, 1]), t+2), convert(n, base, 10));
isprime(add(L[i]*10^(i-1), i=1..nops(L)))
end proc:
select(filter, [seq(i, i=3..1000, 2)]); # Robert Israel, Mar 21 2017

Mathematica

Do[ If[ PrimeQ[ ToExpression[ StringJoin[ ToString /@ (IntegerDigits[Prime[n]] + 2)]]], Print[ Prime[n]]], {n, 1, 500}]
Select[Prime[Range[200]], PrimeQ[FromDigits[Flatten[IntegerDigits/@ (IntegerDigits[ #]+ 2)]]]&] (* Harvey P. Dale, Apr 27 2018 *)

Crossrefs

Sequence in context: A277688 A215131 A355253 * A228471 A062594 A128027

Adjacent sequences: A068987 A068988 A068989 * A068991 A068992 A068993

Keyword

base,easy,nonn

Author

Joseph L. Pe, Mar 12 2002

Extensions

Edited and extended by Robert G. Wilson v, Apr 08 2002

Status

approved